After making most of my hexagons, I sorted them by color and then started arranging them to figure out how many more I needed. My blanket ended up being alternating rows of 13 hexagons and 12 hexagons, with the color changing after 3 rows. I ended up making 225 full hexagons for my blanket (whew!)
ch 4, ss to the first ch to join into a ring
Row 1: ch 3 (counts as the first dc here and throughout), dc 5 times into the ring, turn
If you want a cleaner edge, you can ss across the flat end (I knew I was planning to add a border, so I skipped that step). Fasten off, leaving a 12" tail for sewing.
Once I had all my pieces, I started stitching them together. I sewed the pieces together with a tapestry through the back loops only of each hexagon or half-hexagon. I used the mattress stitch, since I'm rather partial to it and it's never failed me yet.