How buoyant the bait will be is determined by how buoyant the particular wood you choose.
Balsa is so buoyant it lets you make small baits that are still buoyant, but heavier woods need more size to offset the weight of the lip and the hardware.
I think you'll be better off if you make your own blanks from a wood you want to work with, instead of what a store bought blank is made from.
Pick a successful commercially available lure you like, trace it's shape onto a piece of flat shirt cardboard, and cut out a template. You can change the size with a computer program, or you can just trace around the template with a compass, adjusting the opening to make the lure bigger. You can also follow the outline with the compass on the inside, to make it smaller.
Pick a wood you want to use, cut out a couple of blanks, rough shape and sand them, add the lips and hardware, and seal them, so you can begin to test them to see how much and where to put your ballast.
Remember to keep the original lure close by for reference and comparisons.
It's a process that gets shorter with each build, because you'll learn from each one, and that will make the next one that much easier.
You probably won't get it right for the first few you build, but each one will be a little better, as you begin to figure things out.
Good luck, and keep us posted on your progress.