This paper towel box holder has no back side and top side is only for 4 wood screws to screw in the cabinet above. For placing a paper towel box it's made to be accessed with a left hand side sliding door. The screw and wall slide stl's are for adjusting the inside based on the paper towel box so it fits snug. Screw holes at the top are 7mm width with 3mm depth for the screw head and 4mm width for the thread through out.

Bottom has 10mm holes for access with a screw driver.

The towel box must have the wall slide and door stl's added before mounting as this model is used next to a wall as they won't be removable once mounted.

The screw stl  is ornamental. You can model a preferable screw at your choice since this uses a M10x1.5 ISO Metric profile Right hand thread.