Joining entrelac squares

I’m knitting up a bunch of entrelac squares to make a blanket. I started with a provisional crochet cast on of 24 stitches (3 triangles of 8 stitches each) followed by a purl row and knit a total of 7 tiers including the top triangles. I slipped stitches at the end triangles, so joining there isn’t the problem. I couldn’t figure out how to do the top triangles in a way that would give me stitches I can pick up, and since the knit rows are diagonal, I have no idea how to join them to top triangles of other squares.

Also, it’s my first time doing a provisional cast on, so I’m not sure how to pick up those stitches. I tried on one of the squares and ended up not being able to tell where the live stitches are, mostly around the ends and at the places where the second tier begins. Can anyone help?

(Tried to attach pictures, but they’re apparently too large. I’ll upload them to imgur and post the links if that would help)

Welcome to KnittingHelp!
I’m not sure that I understand what you are joining? For the last tier you pick up sts along the side of the rectangles of the previous tier and join by k2tog or ssk on the knit rows. The only difference is that you also decrease sts to form triangles rather than another tier of rectangles. See the end of this video.

What kind of provisional cast on did you use? Some use a crochet chain, others weave over and under a strand of scrap yarn.

Thanks for the welcome! I wasn’t able to post pictures from my phone, and haven’t had computer access recently, so I’m sorry about the late reply.

I uploaded some pictures to imgur:

I have a bunch of these squares, which when blocked will measure 14"x14", and I’m trying to figure out the best way to connect the squares on the bound-off edge, which is pictured.

As for the cast on, the knitting book I have calls it “Crochet Over the Needle Cast On.”

Great looking entrelac.
You can use crochet to join the squares either with a simple single crochet

or something fancier

Grafting or Kitchener stitch would work where you’re joining live sts from the cast on to other live sts but I’m not sure that there’s a way to create live sts on the final tier at the bind off. You might play around with slipping the sts to a holder instead of binding off or knitting two together on each row of the final triangle. I’m not sure if that’s practical however. As I understand it, you’ve already finished the final tier on your squares anyway.

I’ll try what’s in the video, since that extra width would be helpful here.

I’ve been trying to figure out some way to not have those bound-off edges, but it’s tough because the decreases at the edge are what shape the triangle and create the bind off at the same time. In the future when I decrease, instead of slipping the two sts off the LH, I’ll try putting them on a stitch holder to see if that works any better (though, I’m really liking that crochet border, so I might just leave it as is!)
Thanks so much for your help!