Plan: 11 pattern repeats to make afghan a little over 50 inches wide. Initial chain 190 (=17x11 + 3). See below for final dimensions.

Method: I wind leftover yarn into balls “yay” big, allowing for some variability, then line them up into some sequence, and just crochet them up in order, ending the previous wherever, even if mid-row. Great way to use up yarn! The hope is that each ball of yarn can complete at least 2 pattern rows (one of the balls didn’t quite make it here). At most, some were able to complete about 6 pattern rows, noting that the pattern rows alternate between dc and sc.

I decided to square off the top and bottom using a totally new (full) skein and color (creamy yellow), since the afghan was a bit short for my liking, and I wanted to add a bit more. Here’s how I did it (turned out nice!):

TOP, after the sc pattern row, noting that each valley has 5 sts, each hill has 12 sts… going to dec 2 in each valley:
Row 1: 2 sc, 2 hdc, 2 dc; ^(tc2tog, tc, tc2tog, 2 dc, 2 hdc, 4 sc, 2 hdc, 2 dc) repeat from ^ until last 6 sts; 2 dc, 2 hdc, 2 sc. Ch1 and turn.
Row 2: 4 sc, 7 hdc, ^(8 sc, 7 hdc) repeat from ^ until last 4 sts; 4 sc.
Row 3 (optional): Ch1 and turn. 6 sc, 3 hdc, ^(12 sc, 3 hdc) repeat from ^ until last 6 sts; 6 sc.

BOTTOM: a little different from the top because of how I did the extra row of scs here (see notes below and pic):
First, work a row of sc into the other side of the starting chain on the right side. I put 2 scs into the middle “spoke”, and otherwise just one sc into each other chain or chain space. See picture.

Start the squaring off rows AFTER that extra row of scs. Note that on the bottom, each hill has 12 sts (starting and ending with the first and last scs made into the ch spaces), and each valley has 6 sts (in between those ch space sts), along with the 3 sts at the very beginning and end of the row. Going to decrease the valleys down to just 3 sts each.
Row 1: tc, tc2tog, 2 dc, 2 hdc, 4 sc, 2 hdc, 2 dc, ^(3 tc2tog, 2 dc, 2 hdc, 4 sc, 2 hdc, 2 dc) repeat from ^ until last 3 sts; tc2tog, tc. Ch-2 and turn (do not count as a stitch).
Row 2: 4 hdc, 8 sc, ^(7 hdc, 8 sc) repeat from ^ until last 4 sts; 4 hdc.
Row 3 (optional): Ch-2 and turn (do not count as a stitch). 2 hdc, 12 sc, ^(3 hdc, 12 sc) repeat from ^ to last 2 sts; 2 hdc.

Edging: After squaring off the top and bottom (as noted above), I did just two rounds of sc in the same yarn. Along the sides (edging round 1), I put 2 sc in each dc edge, and 1 sc in each sc edge. After all of that, I probably still had enough yarn left to go another round if I wanted to.

Final size was 65” height, 53.5” width.
I LOVE IT.
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My original plan was to do a ridged version as follows (but changed my mind a few rows in since it was going to be too bulky for the amount of yarn I had).. save notes for future:

To add ridges on the RS, I modified row 2 as follows: sc in first st, fphdc across to last st, sc in last st.
Keep row 3 as written. Note - the swatch was crocheted with an I hook (not J). I decided to go up in size given the bulkiness of the front post sts.

I was inspired by the following pattern which I did purchase, but I was confused by the instructions, and maybe because it was written assuming lighter-weight yarn but my modifications create an identical effect:

https://www.ravelry.com/patterns/library/ripple-rainbow-b...