At first I tried placing a heavy object on the material, but she kept moving when I turned on the spindle. When that was not successful I used a variety of “creative clamping” strategies and blue tape / CA glue. I never drill into my spoilboard except when using dowels for double sided part cutting.
First of all note that I have locked in X and Y fences that I can push one or two edges of the material against if necessary.
Plywood with tabbed cutouts are easy to clamp around the edges. Just verify before starting the cut that you will not hit the clamps. Then verify it again…
In some situations I had internal circle cutouts in the plywood (full cut depth) where I would clamp the outside of the ply and cut the inner circles (or whatever shape). When that was complete I would move the clamps to the inner cutouts and cut the outer profile.
If I have a large piece that I want to do a profile cut out on I will clamp one or two sides and do a partial profile. Then move the clamps to the cut profile sides and cut the rest. Keep in mind the direction that the cut will go and clamp accordingly. In other words if I am cutting in the Y axis direction I want a fence or clamps along the X axis to keep the ply from sliding. If you are using finished ply this is even more important as it is a little slippery on the MDF.
I am also a big fan of blue tape and CA glue. It’s amazing how well this holds. You can also use shelf paper in the same fashion for larger areas. Yeah really, it does work! For larger pieces I could use tape squares around the corners to avoid having to tape large areas of the table.
I can clamp to the front of the table as well for a simple way to do end joinery…
Let me know if you have questions!