A clamping fixture for the Demmer 4300.
I referenced the dimensions of the Model 395 Demler sanding machine and used them as a template for the production.
The countertop can be fixed with M5 coarse-threaded bolts
You can either screw the bolt directly into the hole, or first create an M5 internal thread and then install the bolt.

Update:
Base2 can be fixed to the workbench with a clamp.