The blanks usually come in a package like this.
Everything you need is right inside the package. This particular kit is for a 7/8" button. They come in a variety of sizes. In fact my Mom recently purchased some fabric and notions for me at an estate auction. In the box of goodies she sent me there are several sizes of blanks the largest being almost 2 inches. I can't wait to find just the right project for a button that big.
Inside the package you have the following items; a template, a pusher, the backs (with or without a shank), the button top, and the mold for putting it all together.
Start by placing the template over your fabric. Use the center as your guide if you desire a particular part of the fabric to be shown on the button. Trace the outside of the template. I like to trace the inside as well so it's easier to find the center when lining everything up later.
Cut out your fabric circles.
Place your fabric with the wrong side up on the mold. Do your best to center it. This is where tracing the center circle helps.
Place the top part of the button (shell) over the fabric. Again, use the center circle to help you line everything up. The more centered you have it the better for the next step.
Now do your best to tuck all that extra fabric into/over/around the button. This is a step where an extra 3 or 4 fingers would make it easier (especially if you are trying to take pictures of it too), but alas I only have 10 fingers.
Depending on what you plan to do with the button, choose the appropriate back. Place the back of choice over the top of the gathered fabric.
Place the pusher over the top of your fabric button "sandwich". Using all the might you have in the one finger that will fit onto the pusher, push down trying to keep the pressure as even as possible on the back of the button. I have bent the backs before by putting to much pressure on one side or another. Push until you hear/feel a pop-thunk sort of sound.
Pop the buttons out of the mold and there you have it. Fabric buttons perfect for any garment (yes, I know this picture is upside-down).