This pattern from 1888 Weldon’s Practical Needlework, volume 1, will make afghan blocks or stripes. You choose the width and length. The pattern has a 6-stitch repeat. The 20-row repeat has 10 purl rows and lots of identical rows: easier than it seems! I added selvage stitches and a garter stitch border at the beginning and ending of the instructions for an afghan stripe.

Skills needed: long tail cast-on, knit, purl, slip, knit 2 together, SSK, yarn over, slip1-knit2together-pass-slipped-stitch-over (3 stitches decreased to 1) and bind-off in knit stitch.

Gauge: 10 sts/inch and 11.5 rows/inch with #10 crochet thread and U.S. size 2 needles
Gauge is not important. Any block-able thread/yarn and any size needles will work. Make a swatch to check the look and width of your work.

6 yards of #10 crochet cotton makes about 12 rows (1 inch) with a 29-stitch-wide stripe in the above gauge.