When I start a game for a jam, I attempt to get it shipped to the jam as quickly as I can.

Which means:

1. Make a source code repository
2. Make an itch page
3. Make a boilerplate for the game where there is a blank window that I can close
4. Get a build and upload script for the game
5. Ship the game to itch
6. Submit the game to the jam

Many people leave everything other than working on the game's code to the last, and many folks don't use a source code repository.

As a result of this, those folks have to scurry at the end, when if you follow the sort of practice that I outline above, and ship regularly, there is zero stress at the end. You are free to work on yer game.