Stir together the yeast, maple syrup and water in a large bowl. Let it sit for 5 minutes until it starts to foam (if it doesn't, the yeast might be expired).
Mix it all the flour to the yeast mixture until a dough forms.
In another large bowl, add in the olive oil. Place your dough into the bowl and coat it fully in the oil. Cover with plastic wrap and let it sit at room temperature for 8 hours (overnight), until doubled in size. (Don't place it in the fridge, because it will need to come to room temperature anyways before placing it in the oven, in order to bake properly).
Once this done, pick up the edges of the dough farthest from you, lifting it up and over into the center of the bowl. Turn the bowl one quarter and repeat, doing it once each quarter (4 times total).
Next, grease the baking trays with with extra butter. Preheat the oven to 450 degrees F. Lightly grease your hands with oil. Split the dough evenly and place half into each baking tray.
Take the cut olives and onions and press them into both of the doughs, evenly spreading them out. Then dimple both of them with your fingers to create that "focaccia" look.
Once the oven is heated, place the focaccia in the middle rack of the oven for 10 minutes.
In the meantime, heat up a small saucepan over medium-low heat and add in the butter. Once heated, add in the garlic. Cook for a few minutes, until fragrant. If the garlic is browning too quickly, lower the heat. Once this is done, turn off the heat and stir in the Italian seasoning.
10 minutes into baking, open up the oven and with a pastry brush, brush the garlic butter mixture all over the top of both of the focaccia.
Place them back in the oven for another 20 minutes.
Once done, remove from the oven. Let them cool for 20 minutes on a heatproof surface, to let it cook as it cools.
Then cut each focaccia into 8 sections and enjoy! For serving, brush with additional warm butter, if desired.