In a large bowl, mix the dry yeast, sugar, and lukewarm water. Let sit for 5 minutes, until it gets foamy/creamy. - Make sure you check the yeast expiration date before using it. It will not activate if it's expired.
Add the flour and salt. Mix well using a spatula.
Grease a separate bowl with 1 tablespoon of olive oil and pour the dough into it. Turn it and coat it on all sides in oil, then cover it with plastic wrap. Let it rise at room temperature until it doubles its size (~4 hours).
Grease an oven tray with 2 Tablespoons of olive oil.
Transfer the dough to the oven dish and spread it with your fingers. You should either water or grease your hands, to ease the process.
Once it is evenly spread out onto the tray, start poking it with your fingers to form some holes. Add the cherry tomatoes in those holes, drizzle it with 2 tablespoons of olive oil, sprinkle some sea salt flakes on top, and some mixed seeds.
Heat the oven at 220C.
Bake focaccia until golden - for about 20-30 minutes. Serve with fresh basil on top.