You will need the base/wall mounts from @Raybo's Ortlieb bag wall mount.

These bar supports allow the use of dowels for individual clips or longer dowels that span multiple bag widths - giving some more flexibility. See the pictures.

If you're using a very long dowel, then print a through-support provided here. You will still need the @Raybo's designs for the dowel ends.

Printing

Lay flat, mirror end caps as needed, 40% infill is sufficient, 0.15mm.

Assembly

Use 16mm M3 cylindrical screws to bind bar supports to the @Raybo mount plate.
I used 4x16mm countersunk screws to attach the mounting plates to wood.
You will want alternate or longer screws if mounting to plaster or concrete.