The easiest way to do this is to leave the pieces you're meant to punch out in place. In this hole there were pieces I needed for the bookcase, so I did punch those out then replaced them with leftover small pieces of plywood. I then filled in all the gaps with polyfilla. Then lots of sanding, priming then painting. And voila, no more window!
While it slows things down a bit to do these things as you go along I'm glad I did because it would be a lot harder to work on a vertical wall in the house later on. Also while working on this wall I was priming and painting other pieces I needed. This kind of thing is easy, just a bit time consuming.
I had a problem mainly because I had painted it first. So the pieces were sort of gripping each other and I had to try to wiggle/wedge it in place, then wiggle it back out and sand it down (and trim the sides of the tabs), then try again, many many many times.
|The red spots are sticky notes labelling the pieces.|
I also decided that any discrepancy up to around 3/16" is fine. And the gaps will be covered with flooring or filler later on. After working with lots of pieces I realized that's just sometimes as close as I could get to everything fitting together neatly.
I thought I would take a break at this stage but that's not been the case. In my next post, the stairs!