It's finished! I know I tend to take pictures of my feet, but in this case I only did to create a sense of scale. (Although I suppose that's not helpful, because for all you know I might have abnormally small or large feet... [I don't though, they are fairly average].) The rug ended up 40 inches in diameter.
The wool trimmings I cut from the selvages filled a plastic bag, and I only had a tiny bit of the selvage leftover (you might be able to see the mini ball by the crochet hook) once I finished the last row.
For those interested in how I actually crocheted it:
I started with ch 2 and worked in continuous rounds
Rnd 1- 7 sc in second ch from hook
Rnd 2- Working in back loops only for entire rug, 2 sc in each st around
Rnd 3- (sc 1, 2 sc) around
Rnd 4- (sc 2, 2 sc) around
Rnd 5- (sc 3, 2 sc) around
.... continued with this pattern, adding one more sc between (2 sc) in each round, up to (sc 11, 2 sc). I also tried to stagger the increases (2 sc), for a more round shape.
It crocheted up fairly quickly even though it was a bit of a workout for the arms! It was also a lot of fun using the massive 25mm hook!
Have you made any rugs?