Flat pack, self assembly furniture was created by Satan himself.

If you are buying a self-assembly unit for an alcove, measure both the top, middle and bottom of the alcove, because 40+ years ago, builders could not make a wall in a straight line; it will get narrower towards the top and the d*%m thing won't fit.

Invest in a plane*

Make sure to have a good supply of plasters on hand.

*Woodworking tool, not a jet.