Ok, I’ve had some requests for directions, since I am not in the craft, crocheting book writing business, this will be very “non-technical.”
First start a very loose single crochet chain about 1/3 of the length of the finished rug or a bit longer.
When you get to the end of the chain, turn and make a single crochet into the last chain, repeat into this same hole about 4-5 times to make a curved edge. This will make the basis for your oval end of the rug. Then repeat the single crocheting back along the chain until you get to the first stitch. Repeat the 4-5 single crochet stitches into that hole, and then single crochet back in the first direction.
(Oh, I hope that makes sense, I am really by no means a tutorial-writer.)
As you repeat this process around and around the rug you will keep it straight on the sides and add stitches around the ends of the oval to keep it flat. Add the same amount on each end to keep the shape symmetrical. This doesn’t need to be exactly precise, like counting stitches or anything, just add 3 or so on each end, to make it curve.
I didn't like the way the dark blue fabric stitched up. It is nylon tricot knit and the others are woven cotton/poly blend. You really should keep your fabrics the same weight and type. I'm still debating if I should tear it out and remove the blue or just leave it. It is more "holey" than the other ones, so someone may snag a toe and crack their head open on a dresser. (Come to think of it, with all the injuries around here, I'm tearing it out now.)
This crocheting takes a lot of shoulder and arm work and you may be sore after stitching for a while. I stitch around and then do shoulder rolls to keep my muscles loosened up, it is really quite a workout.