Prior to pinning - cut off slottatab with snips, zona saw, etc. File or sand undersides of mini's feet to a flat surface for mounting of pins.
Models with integral bases require slightly more work - cut away as much of the tab as possible with snips before filing away remainder of excess metal.
NB All following stages can be replaced by cutting away enough of the miniature's slottatab to leave a peg under each foot; this will require larger holes to be made into the resin base but will essentially follow the same procedure otherwise.