Magnetic Corner and Edge Hold Downs for Laser Honeycombs
Previously used large (25mmx3mm) magnets (on their own) but after dropping 2 magnets and shattering them a 'better' option was needed. Only "affects" 3mm of cutting area around the edges.

My honeycomb has aluminium frame but honeycomb is some type (?) of steel which protrudes into honeycomb frame housing, therefore magnets still work on the edges.

Magnets used were 10mm diameter by 3mm thick
Hold down "lip" is 2mm high and specific for my Honeycomb and 3.175mm thick MDF sheets.
Adjust to suit your own requirements

Model files with "WSup"suffix have integrated support for the Magnet cylinder holes. Depending on your nozzle size and printer settings the support may be ignored by your slicer.
Use the integrated support models only if your slicer does not bridge gaps well or your support is difficult to remove.

"Floor' of the magnet holders is 1mm thick so can be reamed 'deeper' for maximum magnetism effect.

Hold downs could be potentially laser cut and ridges / blind holes (progressively) engraved but may take longer that way. Alternatively you could design and cut the hold downs using multiple thicknesses of material and glue together.

Warning: Magnets are potentially dangerous. Use with care.