I've found wood screws work well for this. The wood screw can cut its own threads without needing to use a tap.
It does put some stress on the part, though. I mostly print in PETG, which is strong enough; but PLA might split if the hole was parallel to the layers.
> A design limitation of threaded inserts is that they are not reliably usable for screws inserted from the back side. During insertion, heat-set inserts often push some molten plastic into the hole beneath them, preventing easy insertion of a screw from the back side.
A trick I sometimes use:
1. Before installing the insert, insert the screw from the back side
2. Screw the insert onto the protruding screw
3. Use a soldering iron to install the insert+screw together into the plastic
Because the screw is filling the hole, the molten plastic can't block the hole. Instead, the molten plastic forms itself around the screw, and it acts like a Nyloc nut.