What did you have to do to get it to fit?
Well, I had to make the box considerably narrower than the space because the space is out of square, and the front wall is not all in the same plane, top to bottom and side to side. So I made the side stiles wider than the front opening, and I had to use my block plane to shave them to fit. Figured maple is not the easiest wood to plane cleanly. I got my blade extra sharp and it did well, but it is difficult work. I had to set the cabinet into the space, note the fit at the front, then remove it again, tip it on the side, plane it, fit again, remove, plane the other side,....By the time I was done, I had a 1" setback from the front walls to the cabinet face, on 3 corners, and 7/8" on the lower left corner. Meanwhile at the back of the cabinet, the left side was an inch from the left wall and the right side was 2 1/8" from the right wall. And this was all done without the top on. I fit the top before I even did the finish sanding.
The side walls at the top were concave, which meant that I had to plane the end grain of figured maple. It was hard work and took quite awhile. I had to set the left end in place, almost touching the back wall, and lower the right side down, determining where I needed to plane. And the back wall was convex. In the end, I got the top to fit with no more than 1/32" gap around it.