So there's two skeins of worsted weight wool. I'm thinking about a size I crochet hook (5.5 mm).
One way to go is to make a rectangle for the outside, fold and sew it, and add pockets and straps. That sounds too boxy and too much sewing.
I'm more in the mood for making a big piece that I fold and stitch and then add gusset/straps in one fell swoop. The one big piece would be fairly mindless to stitch, so I could do it while walking my dog (he walks slowly and stops to sniff). Then the other parts wouldn't take much time at all.
So -- for the big piece. An Octagon would be fun. That's 8 sides, or increase points. Crochet lies flat at 6 increase points in single crochet or about 12 increase points in double crochet. This is great because I want to use crocheted seed stitch, increasing 16 stitches every two rounds.
Crocheted seed stitch: (sc, dc) across, then in the next row/round, sc into the dc and dc into the sc. I'll start in the center with (ch3, slip stitch to form a ring), then (ch1, sc1 into the ring) 8 times to start a coil in the next round. It makes a fabric that is more solid than double crochet and doesn't stretch out of shape like single crochet.
Now I need to get started!