I just use screws and clamps. I use the plastic printed hold downs where I think the router might go, the metal ones I use where I know the router will not get close, or where the dust shoe has to pass over.
I have also used superglue and painter’s tape. Put tape on your spoil board and on your material being cut. Then a bunch of superglue on one piece of tape and spray quickset on the other. Press the two pieces of tape together and hold for a second. So far nothing has come off, and even if your tabs get cut off, inside cut out pieces will stay attached.
This is how I attached the piece of acrylic in this video.