It's no secret, people have been building DIY Camera dollies for a long time. You can follow the instructions on the video above, but in my experience, it's a bit tricky to get things lined up perfectly. If you don't have it aligned correctly you get a little wobble or binding in your movement. If you want to save yourself some time and money you can buy pre-built dolly wheels here, and then just get a piece of wood for the stage.

Swiveling Caster Video Dolly Track Wheels