Can I prepare Focaccia today, but bake it tomorrow?

Yes, possibly if you know how to control the fermenation variables .... if you use lesser amount of yeast ,, preferabley use a dough enhancer ,.. cover the pan (with dough on it )with polythene... and let it rises slowly in refirgerated conditions. take out from the fridge....place your desired topping, and bake....

If time permits your best option is to mix the dough , place it in a bowl for the first rise, refridgerate it overnight.

Next day , take it out, punch it down, form the bread, pan, let rise, bake.

I'm baking German breads with self made sourdough only (no commercial yeast). And I always prepare the dough in the evening and leave it over night in a warm place, covered with a cloth.

Greetings Jens

Thanks, I'll give that a try. Happy 4th!