what u need to purchase is inch thick balsa wood. Cut them to what ever length u want. Then shape them, make the bottom pointy while the top rounded,(shape them like a drennan) paint the top red or orange then put 2 coats of clear coat varnish. To make the line run through buy some plastic tubing thick enough to fit a tooth pick snuggly inside. Drill a hole just big enough to fit it, so it wont come out make the hole fit around the plastic tubing very snug.(balsa wood is extremly soft so if the hole is just a little too small u might be able to get away with working the plastic in) thread the line and put half a tooth pick in each end as bobber stoppers and vualla, balsa float. A lathe and sand paper are ur two main tools. Shape them to the size and width u want. Usually my floats are 1 inch wide and 5-6 inches long depending on the size and colour of the river. They look like a piece of wood floating so they dont spook fish, just paint the top no need for the bottom! They are super sensitive and dont crack. They are the only ones i use for steelies! If u find that u can make them another way do so, my way is my way, dont stick to it, experiment!
Good luck and good fishing