I use one inch wide, glass fiber packing tape, to hold my router jigs in place. I started doing that, in 1969. I’m getting ready to do it again, next week. It works very well for me.
I’m routing a glassed board, since I rarely mortise anything before glassing. I use masking tape, or duct tape, and often clamps also, but the soft tip kind, and not clamped tight enough to mash the foam.
I have some thin plywood jigs that I secure with masking tape. Actually, I reuse tape and have it stuck all over my shop. Tape is expensive. When I pull tape off of a set of fins that are set in resin, I save the good part and reuse to scim a glassed board for dust and particles before the fill coat or the sealer coat.
To secure the jig I have also used wide mouth clamps with small pieces of thin plywood cushioned with a piece of foam against the board. No denting.
The smaller 4" future jig I hold by hand with the traction stuff that came on the jig like the cabinet stuff you use. I will assist with the hold down with persons learning the technique. Pic of 11 year old that fiqured it out without assistance/ and leash plug plunge also
I’ve had issues with the antislip pads for drawers or under rugs, leaving marks on Cedar sanded to 180 , and no longer allow it to touch surfaces which will later see resin. I’ve also seen a perfect fish eye pattern the same shape as the antislip pattern, when I Did not wipe with DNA or IPA, on a cured resin surface.
When it gets dusty it’s antislip properties diminish greatly, and the whole time it is exposed to workshop air, absorbing potential secondary bonding inhibitors.
I glue various grit sandpaper to flexible jig footings. I also use clamps and weight. I have some old 3 and 4Lb lead fishing weights, covered in many layers of masking tape which are amazingly useful, and I will use clamps too, and use a piece of wood to bend to the deck’s convex, and spread the load, and keep clamp from slipping off, Though this can add tons of time to the process.
Belt, suspenders, and duct tape too for good measure. A slipped jig is not worth the result of having not used all Immobilizing methods, in combination, as possible, in my opinion. A slipped jig can have the router rip from your hands and shoot across the board into the wall, and better the wall than your belly.
Get a Router speed controller. I usually start mine on speed 10.5 out of 12 for best control, then adjust accordingly. Ideal speed depends on the wood and the depth of the cut and sharpness of the bit, or for blanks the density of the foam and the glass, if routing through both glass and foam in one pass. I find that max power then plunging and then determining push/removal rate is much harder and more stressful than starting somewhat slower, and then dialing up power to find the sweet spot in terms of precision and ease of attaining that ideal. Quieter too.
It’s been said a lot already, but tape. I use whatever is handy at the time. The double sided tape that most wood workers have/use is awesome.
I also wouldn’t dismiss clamps either. A couple pieces of scrap foam, wood, plastic, etc under the clamp pads to spread the pressure should prevent any dents in the foam.