This is a really simple bracket you can use with any of my printed stages (see my profile). It allows you to bolt them down to a surface and only needs 2 M3 bolts to be secured to any side of any of the stages. You can find designs and instructions for this and other items in the ecosystem on my website:
https://www.tomsvault.org/My+Projects/Easy+Stages/Other+Addons/Easy+Stage+Side+Mounting+Brackets
You can find this design and the others in the ecosystem on my GitHub (linked below) where the most up-to-date versions can be found.
The author marked this model as their own original creation.