Open XCS file, cut out the pieces.  There are two sizes of square piece in the file, the red (0.320 inch square) and the blue (0.330 inch square).  The blue are ignored in the XCS file as I found them to be just a bit too big.  You may wish to play around to fit the exact dimensions of your honeycomb base.
 

The idea behind this is that you will glue four square pieces to a #6-32 bolt that's an inch long.  This assembly will drop into the honeycomb base holes if the points are aligned one way, but when you turn the piece with the little wrench by 45 degrees, then the points of the acrylic square will push against the honeycomb material and make a friction fit.

As seen in the cover photo, I've got a nasty piece of basswood that is badly warped, and the magnetic clamps just can't overcome it.  These devices can help.

Slide the four squares onto the #6-32 bolt.  Put on a piece of paper.  Glue each square in turn from the head outwards.  Use toothpicks to move the pieces, don't glue your skin.  They are little squares so will self-align if done on a piece of paper on a flat table. I use a spritz bottle with 91% isopropyl alcohol as an accelerant, but use of a hair dryer to set the glue is still recommended.  The alcohol is a big help as it will turn the super glue white so you know where it is.

Ensure that the super glue is dribbled onto the threads of the screw between the pieces, so do them one at a time.  Also put some extra glue over the head of the bolt, and on the threads where the fourth square is, to ensure that not only are the four pieces bonded strongly to each other but also to the bolt.

put a clamping piece (couple shapes in file, make your own as you like) on the glued assembly and loosely put a nut on it.  drop the assembly into the honeycomb with the points of the squares left-right and up-down.  It will drop easily.  

Adjust so that one of the acrylic squares is above the honeycomb panel, the other three inside.  Slide in the wrench at 45 degrees.

Then turn the wrench 45 degrees until the wrench is aligned horizontally with the panel.  The ‘points’ will now be pressing against the formed steel walls of the hole, making a friction fit.  

Then you can hold down your piece and tighten the nut finger-tight to clamp. These clamps will relieve, like the magnetic ones, but they're stiffer.

There will be inevitable tweaking due to variations in honeycomb panels, how much glue you use, and other factors.  the 0.320" size fit nicely in my honeycomb panel but the 0.330" size was too big and would not fit into the holes.  You may want to try changing the size of the squares or wrapping a bit of tape around the glued assembly.

This is not going to hold anything, but I find that these have significantly more holding power than the magnet clamps.  Plus, you can cut the clamping pieces to whatever size or shape you want.  when reusing a piece of plywood that already has holes in it, these clamps are also small enough to be put in place first and then you put the plywood over the bolt and then thread the clamp and nut on.  So they also can fit in tighter spots or be used in the middle of a piece where the other clamps maybe can't be used.