1. Trace your sanding pad on a piece of plywood. 2. Find the center point of the circle and cut it out with a router circle jig. Make shallow cuts in multiple passes. Plans for the Router Circle Jig are free. 3. Enlarge the center hole and insert a threaded insert. Thread in an m8 threaded rod, which will be used as a driving shaft. (For higher precision I suggest using a steel shaft instead of the threaded rod attached to the playwod disc using a Flange Coupling Connector with a grub screw.) 4. Trace out the plywood base plate. 5. Cut out the inner corners with a 35mm forstner bit. 6. Cut out the straight lines using a jigsaw. 7. On a piece of wood, mark out and drill the holes for the rod and bearings. Make sure the holes are alligned PERFECTLY (the use of a drill press is recommended). 8. Press the bearings into the corresponding bearing holes. If using a hammer, try hitting only the outer bearing races so you don't damage the bearings. 9. Insert the sanding drum into the bearing guides and attach the hand drill chuck on the other side. 10. Flatten the front face of the disc using sandpaper on a straight piece of wood. 11. Glue velcro hooks on the disc and cut out the excess. 12. Attach a mesh sanding pad of desired grit (I usually use 80, 120, and 180 grits). 13. When using, make sure the base plate, bearing plank, and the drill itself are all FIRMLY attached with clamps. I use 1st gear at max rpm for sanding.