Hey stradibarrius,
as for uploading photos, I answered here.
Regarding alignment of a two-sided part, you usually make a frame that holds your workpiece that has two or more circular wood dowel holes. You can also make that the workpiece itself has the dowel holes. It is important that the dowel holes are drilled by your CNC and that they go through entire frame/workpiece. Then you drill the corresponding holes into your wasteboard, or into a surface you put on top of it, and place dowels into the holes. Works good with 6 or 8 mm dowels.
Video of cnc-milling a two-sided part (keyword “reference holes”)
@BillG already explained the wood dowel method in your other thread