The rug will want to buckle unless you double tuck the "tuck-in" strand into the rug when going around the corners. The rug needs to grow, which requires more places for braids to tuck in. Otherwise, my rug would look like a floppy bowl. Even with carefully placed extra tucks in the same holes, the rug is a little wavy.
The rug is tighter than a crocheted version, but places where I experimented with double tuck-ins are a little bulkier than others. The back of the rug has an oval knot pattern for every circular pass around the perimeter. It's a little difficult to tell in the photo, but I can certainly feel the rows of raised "tuck in" points.
A small rug can be made within an hour or two; little trivets in maybe as few as 15 minutes! A large rug however eats much more time, especially as the circumference of the rug increases and it seems to take 30 minutes or more just to add one new row around the rug. I thought the rug was big enough, until I took this photo and realized I would like about 6" more on each side. I know how I'll be spending whatever downtime I have for the next week to get this project completely done!