Technically, these are 21-row slippers since I worked two extra rows (and am glad I did). They fit perfectly. I don’t like the look of the lines caused by the decreases. Next time I make these I’ll stitch it up somehow before I felt it. Or I’ll alternate the placement of the decreases (although that might screw up the shaping).
The yarn you see in the photo was all used up sewing these together. I literally had 4 inches left.