This is a simple design that can be used with D&D miniatures. The D&D figure fits on top of the marker and markers can stack on top of each other.

For smaller bases, you can flip the marker and place the figure within the opening.

Print in different colors to represent different kinds of markers.

The markers fit together loosely, and Sticky Tack (e.g. for holding up paper or posters) can be used to hold in position if desired.

I am considering making these for larger bases, but you can always use the OpenSCAD file to make your own.