Very simply mount, that will fit on onto an extrusion frame.
Holes for mounting to 2020 extrusion are M5 sized.
Holes for Duet board are m3.
[Minor update 1]: I made a small mistake on the screw recess. Updated in v1.3.1.
[ Update ]: Added added v1.4 which basically makes the bottom flush with the edge of the extrusion instead of going past it.