The short answer
Rehire the people who showed up on time, were easy to work with, and did not need watching. A worker who already knows your site starts an hour ahead of a stranger, and a short list of four or five people you can call is the most valuable thing you build on this platform.
What actually makes somebody worth rehiring
Three things, and none of them is speed. They arrived when they said. They were easy to be around. You did not have to watch them.
Speed is nice, but somebody steady who needs no supervision is worth more across a whole day than somebody fast who needs directing every twenty minutes.
The hour you save
A returning worker does not need the walkaround, does not need the boundaries explained, and knows where the tools live. On a five hour job that is a real share of the day.
They also make a new person productive faster, because now you have somebody who can show them instead of you doing it.
Tell them at the end of the day
The moment to say it is while they are still standing there. "I have another one in two weeks, can I message you?" Almost nobody says no.
Then leave the review that day, while you remember what they actually did. It helps them and it keeps your own list honest.
Build a bench of four or five
One good worker is a person who is sometimes busy. Four or five is a crew you can actually staff from.
Message them directly when you post, and give them a little notice. People who can plan around your work will keep saying yes.
Keeping them
Pay on time, every time, the way you said you would. That one habit does more for your rehire rate than anything else on this page.
Pay at or a little above the local rate, be clear about the day, and be somebody worth working for. The people who do this get their first choice of workers, and everybody else picks from who is left.
When not to rehire
Do not bring back somebody who was unsafe, who was drinking, or who was hard on the rest of the crew. One difficult person costs you more than the labor is worth.
Say it plainly if they ask, and leave the honest review. Both of those are how this stays useful for the next employer.
One thing to watch as it grows
The more regularly you hire the same people, on your schedule, with your tools, the more the arrangement starts to look like employment rather than contract work.
That is not a reason to stop. It is a reason to read the guide on employee or independent contractor and to have a short conversation with your accountant and your insurance agent.
This guide is general information, not legal, tax, or insurance advice. Rules differ by state and by situation, so talk to your own professional before you rely on it.