Silicone is not my material of choice for baking bread, cakes or muffins in. It doesn't radiate or hold heat like metal does so you don't get as good results. Bread (and cakes) cooked in a metal pan will have a better oven spring (rise) which means the texture will, in turn, be better (lighter) and the bread/cake will get a more golden crust.
That instant and radiating heat is so important.
You could use Pyrex. It would be a better choice than silicone but again it doesn't radiate heat like metal does. Cast iron is a great choice though. I often bake my focaccia in a cast-iron skillet because I love the crusty bottom it gives.
You can bake this focaccia on a regular old baking sheet too if you want to. Line it with parchment paper if you aren't sure if it will stick, and pour the dough on and spread it out with oiled fingers. It will end up a bit thinner so won't need quite as long in the oven. Knock off 5 to 7 minutes.
Hope that helps!

You can omit the oil. Obviously it will affect the flavour though, but if you're used to oil-free it will likely be ok for you. Warning though, oil acts as a softener and preservative in bread so the bread will be crustier (not necessarily a bad thing!) and it will stale a lot quicker. Hope that helps!

It hasn't been tested with gluten-free flour. I doubt very much it would work though. Sorry :O(
I have been working on some gluten-free bread recipes but they aren't going so well right now though. Hopefully one day I'll have something good enough to share!

I'm so pleased you enjoyed it! The more olive oil the better in my opinion! ;O)

Mine doubled really quickly too but I let it set out for the rest of the time anyways because I really wanted it to turn out and mine didn’t fall at all :)