I designed this and shared it on thinkercad several months ago but never took the time to upload it here. Now thats fixed.
The holes on the back are designed to add more grip for the glue.
If you use hot glue it doesnt matter but with other glue, fill the holes and the surface with your glue and then apply to your item.
You can edit it on thickercad
If you have problems with the part getting kicked off the bed, use a brim.