Cut and shape your body material to the desired form. Size depends on the buoyancy of the material and the desired sensitivity. A catfish float that will be larger and less sensitive, but you will be able to cast it farther because it will hold more weight. Cork is more dense than balsa so the same sized float of the same material will not react the same. Trial and error is the only way I know to figure this out, unless you have a degree in Physics.
Drill a hole as close to center as possible through the center of the body. You can make corrections with a little more shaping later.
Cut your stick to the desired length, this again is dependent on the intended use. Longer floats are usually better suited to dipping with a long pole. Shorter floats usually cast better with less chance of tangling. I glue the stick in place with water resistant wood glue or a super glue. I like the mast to be shorter than the keel this seems to make them stand up quicker with the least amount of weight.
The style I make has a eye on the keel end. I use a very small safety pin with the clasp and the pointy end cut off. I use thread to wrap the legs to the stick and a touch of super glue to hold in place. You can also make simple loop out of just about any stiff wire. Try to get one that will not rust.
Now you can finish your float anyway you want. I like to keep the natural colors of the materials. But you can paint them bright colors if you want. I then dip mine in polyurethane to water proof.
The only thing left is the keeper at the top. I use a silicone tubing used on archery peep sights. It won't dry rot. Rubber band and surgical tubing can be used.
Try these simple floats and you enjoy seeing them disappear as much as I do.