How do I make skirting boards removable?
You could do the following:


Cut skirting board to size
Attached it to the wall with glue-on hook and loop tape (often called by the brand name Velcro®) 
Cut and place a thinner quarter round or ogee molding along the top edge of the skirting, conforming it to the curves in the wall
Attach top molding with glue and brads, only to the skirting, being carefull not to get any glue on walls (masking tape or waxed paper can be used)
After glue dries, remove skirting/moulding unit
Paint skirting/moulding unit
Reinstall.