How do you start the hexes?

There are quite a few ways to start off a flat knit piece done both in the round and center out. I keep gravitating back to the I-cord method. This piece is a hex, so I start by casting on a three-stitch I-cord, and working one round (I'd start off an octagon with four stitches). On the second round of the I-cord, I take my first needle and knit one, then make an increase in the space between the just worked and next stitch. If I want a more open center I'll do a YO. If I want a more solidly filled center, I'll do a make 1 lifted bar increase (a devil to do on the second round of an I-cord). Then I'll take another needle and repeat the K1, increase 1 unit. And again on a third needle. Now I have three needles in the work, each bearing two stitches, plus one in the hand to work with. At this point I flip over and begin following my pattern. For an octagon, I'd do much the same, but with a set of five instead of four needles.

Why bother with the multiple units when you can just assemble the hexes into a perfectly good counterpane?

For pretty much the same reason I make cassoulet instead of being happy with franks and beans.

How big are your motifs?? How many are you planning on making?

It's difficult to get a gauge on this stuff, but if forced, I'd say I'm getting approximately 6 stitches and 8 rows per inch over the stockinette areas. Unblocked, my center most hexes are about 10 inches across at the widest point. The squares are about 5.5 inches on a side. The bases of the triangles are also about 5.5 inches across. One entire meta-unit of hex surrounded by squares and triangles (unblocked) is about 21 inches across. I haven't measured my bed yet, but it's only a queen size. Given the vague bed linen sizes posted here and there, my counterpane should be a square or a rectangle something between 85 and 100 inches on a side. I'll need at least 4 units across and 5 units head to foot. Given my chosen layout, that's about four rows of four units, plus three rows of three units, or 28 units. That adds up to 28 hexes plus 168 squares and 168 triangles. Plus half hexes, and the smaller units needed to square out the edges somewhat (they're never going to be exactly linear), and an edging of some unknown depth. I'm not quite sure how many of the other shapes I'll need yet.

Doing the same size counterpane using only the hex units would mean making about 10 rows of 8 units, and 9 rows of 7 units - that's 142 hexes, plus edge half hexes and a border.

This project should keep me busy for a while.