I should have also asked, what type of border would work best for them?

And I should have included the photos. Below is what they look like.

Additionally, maybe I'm crocheting too tightly. So how do I loosen up my stitches, or should I just go to a bigger size hook?

Thanks!

Your crochet looks fine to me. I'd just run rows of single or double crochet around the outside until they are as large as you want. Do 2 or 3 stitches in each corner and a couple in the end of each row. You may have to experiment a bit to figure out how many to do in the row ends so the border will lie flat.

Donna

The first Donna gave you good information about the increases on each round. And since this is your first project, she's right about the single crochet. That would be your best bet. Later you can try something a little different. As to how to start when you've already woven your ends in, that's no problem. Just start with one chain, then begin with a single crochet anywhere you like, then continue around (don't forget those increases at the corners - I'd do three in the corners), slip stitch to your beginning sc, ch 1, then do it all again. Do as many rounds as you need to make it the size you want. Good luck!