Garter all around
to do this I do a certain number of rows at the bottom in garter stitch. I then knit a certain number of stitches on the left and right side in garter stitch. Then after I do as much stockinette as I want I do the same number of rows in garter at the top as I did at the bottom. That little bit of garter all around really helps with the curling and to me makes kind of a nice frame for the stockinette and also an even depth in the fabric.