CO 40 using knitted caston for looseness.
Five base triangles for a 16” wide piece.
(14” in its lumpy, unblocked state)

Usually I prefer straight needles for entrelac, for narrower scarves, keeps the work flat. But for this width project I’m using 32” circulars.

I have detailed notes on my other entrelac project pages.

Basically:
Tier1: L to R, has side triangles, PUAP with p2tog and sl on join rows (p)
Tier2: R to L, all rectangles, PUAK with SSK and sl on join rows (k)

Knitting backward instead of purling comes in very handy for the base triangles when the rows are so short, but otherwise I find it easier not to.

On the last PUAP on Tier 1, the last picked up stitch should be in the bump at the very edge of the work, otherwise you get a jagged looking right side edge. You can pick up 9 stitches if necessary to get all the way out to that edge, and decrease one away on the next row.

Edging: Two rows of half double crochet to create a firm edge. Then Cathedral Edging 8 clusters across.

The piece including edging measures 40” x 14” unblocked.