In my expirence with that kind of setup (bettas and cories), you just put the flakes on the surface, and then when the betta is eating the flakes, drop the algae wafer (or whatever you are going to use) or piece of an algae wafer on the opposite side you feed your betta on.
I don't recommend any species of tetra with a betta in a 10g tank. A common pleco can grow to be well over 2' long, and require a 75g tank minimally. There are smaller species of pleco such as the bristle nose and rubber lip plecos. They aquire a small adult size, but imo they need a 15g tank or better.
Mollies can be fin-nippers (as many livebearers tend to be), so if you put them with a betta, you have to closely and regularly examine the betta's fins. I also don't recommend mollys and bettas in a 10g tank.
Don't worry, we'll figure something out.