Fixing broken/missing screw bosses on plastic parts

Looks like about 1/3 of the hole remains. I wouldn't try to rebuild the missing portion. Any pressure from a screw would just crack it again. Instead I would remove the rest of it to a L shaped mating surface with a well roughed surface for bond tooth. Then build the boss with Plasticast which is basically the same as making your abs paste like described above. Drill proper size hole for screw in new boss.