I had a need for the standard .883" riser, but the small .883" boxes weren’t providing the stability I needed for a largish plaque. I spun this up to give me another option when engraving wider plaques that are too thick for the crumb tray. The original design uses six magnets as you can see, but after trying it out I thought more magnets would make it less likely to move, so I added them in the final design. On my machine, with kerf accounted for, this comes out right at .883", but YMMV, so test a smaller chunk first. I also recommend a double engrave of the circles so the magnets sit down nice. This was done in Inkscape if you need to convert it to some other format.
When your workpiece is over .5" tall, but less than 2", you can remove the crumb tray, but you have elevate the workpiece into the 0-.5" range. Many of us use .883" risers of some kind to accomplish that. Read all about it here.