How do I bring it all together?

Welcome to the Block!

One thing I have been tinkering with is organic in-character intros. It's just like you describe: how do the players relate, and what kind of story is ahead of them?

I was introduced to the concept of the Phase Trio, but I didn't understand it. I'm trying to use it now.

Essentially, each player describes their first adventure. They write down the beginning on a card of sheet, and pass it to another player.

Here's where it gets good.

The second player describes how their character crosses paths in the course of their own adventure or played a minor role in the first player tale.

Repeat this a third time so 2 other characters appear in each vignette.

The players should use or showcase a personality trait, an ideal, and a flaw for the beginning, middle and end. The outcome of this method would create bonds with other characters.

All of this can get used again and again.

The Bonds can be used to gain inspiration in play, drawing back on shared backstory.

The adventures should generate NPCs or factions or plotlines you the DM can pick up and use; the players are already hooked in.

I hope this is a useful idea. It might be a little janky to inject if the players are already rolling in a scene; it's better for session 0.

You can find the details on the concept here:

Here's the flavor sections they use to demonstrate it in action:

Ask yourself the following story questions. If you have trouble answering them, talk to the other players and the GM for help.
Something bad happened. What was it? Did it happen to you, to someone you cared about, or to someone that you were coerced into helping?
What did you decide to do about the problem? What goal did you pursue?
Who stood against you? Did you expect the opposition you got? Did some of it come out of nowhere?
Did you win? Did you lose? Either way, what consequences arose from the outcome?
Once you’ve come up with the adventure, write an aspect that relates to some part of what happened.

Player 1 goes through Phase One. He looks at the story questions to help him figure out the events of the phase, and decides on the following:

The bad thing was that Landon kept getting into scrapes at his local tavern. He grew up with no sense of discipline or demeanor and constantly picked fights with people larger and stronger than him.
One thug Landon insulted at the tavern was connected to the Scar Triad, so some of the thug’s bandit buddies showed up and beat Landon to within an inch of his life.
His bleeding body was then found by a veteran soldier named Finn who healed Landon’s wounds and encouraged him to join the town militia where he could learn some discipline and fight with honor.

Now Lenny has to write down a character bond related to this story. He decides to take I Owe Old Finn Everything as his bond, because he wants to keep the connection to Finn in his story and give the DM a cool NPC to play.

Phase Two: Crossing Paths

Complicating the adventure: Your character managed to make some part of the adventure uncertain (possibly because of an ideal of flaw). Of course, since that happened in the past, it is known that you got out of it all right (or mostly all right, as indicated by the aspect you take). When describing this, don’t worry about how the situation is resolved—leave that for someone else, or leave it open. Descriptions like “Landon starts trouble when Cynere needs him quiet” or “Zird gets captured by mysterious brigands” are enough to get some ideas flowing.

Solving a situation: Your character somehow solves a complication that the main character in the adventure had to deal with, or your character aids the main character in the central conflict (which is an opportunity to involve a personality trait). When describing this, you don’t have to mention how the situation was created, just how your character takes care of it. Descriptions like “Cynere holds off foes to give Landon time to escape” or “Zird uses his arcane knowledge to ask the ghosts for information” are enough to give us an idea of what happens.

Complicating and solving: Here, your character either solves one situation but creates another, or creates a situation but later solves a different one. Mash up the two ideas, using the word “later” in between them, such as: “Landon starts a fight with the Scar Triad while Zird is trying to lay low. Later, he helps Zird by fighting off undead while Zird’s casting a spell.”

Player 2 has Player 1's starting adventure and needs to decide how she fits into it.

She decides that Cynere helped solve the situation. After Landon ends up in the militia, he still has a grudge against the Triad members who ganged up on him. In fact, they robbed him of his heirloom sword in the process. Hearing Landon’s tale of woe, Cynere agrees to help steal the sword back.

She takes the flaw A Sucker for a Sob Story, to reflect the reason why she got involved.

Landon gets into a bar fight with some of the Scar Triad. He is robbed of his sword and beaten severely. His life is saved by a veteran soldier named Old Finn. Finn helps to heal Landon, clean him up, and enlist him in the town militia.

* I Owe Old Finn Everything
When Landon tells Cynere his story, she takes pity on him and decides to help him recover his lost sword.

* A Sucker for a Sob Story

Player 2 gets Player 3's starting adventure, a pretty straightforward romp where Zird battles his Collegia rivals to obtain a magical artifact and return it to its rightful place.

She decides that she complicates that situation, by wanting the shiny artifact for herself. Player 3 already established that Zird gets the artifact back to where it belongs, so she only holds it temporarily.

She decides to take the bond I’ve Got Zird’s Back, as a way of reflecting her willingness to stick her neck out for Zird—the group doesn’t know what he did to earn such loyalty, but they figure they’ll find out eventually.

Cynere steals Zird’s artifact. Eventually it returns to Zird’s hands and the two gain a mutual respect for each other.

* I’ve Got Zird’s Back
And with that, you have personality, ideals, bonds, flaws and a good chunk of background!