a website with good suggestions.
https://www.stitchingthenightaway.co...stitch-pieces/

This link says to lay the quilt top onto the batting "right side down". That can't be right. It also says to cut the batt the same size as the top before you stitch them together. I think that's asking for trouble.

The work you show is beautiful. I once made afghan squares separated by a thin line of black. It is stunning and I enjoy it every day as it is always on my bed as a bedspread sometimes used as an extra blanket. It is made of wool, so is very warm and very heavy.

You will certainly need some kind of sashing, and it really should be the same color throughout, so I was thinking about a beautiful green or blue, probably in tone on tone. But consider the thin black lines. Lay it out and test it to see how you like it.

I would worry about how much washing it could stand.

Wow! What a thing of beauty! I can't imagine the work -- and hours -- that went into this. It's stunning!

Thank you everyone. The screen took me about a year, on and off.

I've cut everything to the same size, laid it out to get the squares in an order I like. I'm in the process of washing all the squares again as some have been in storage a long time, soak in very hot water and Biotex, roll in a towel and the iron with a hot iron on the wrong side, it works really well so I can't see washing it will be a problem in the future.

I'm just waiting for the batting and the backing fabric to arrive, plain white cotton as I don't want to detract from the squares.

I have enough squares for another quilt too - oh boy!

Hopefully I can post an update by the end of the week - the joys of being retired:o

If I’m understanding you correctly, google the Mario pixel quilt BOM. There’s a blog post that goes into the technique. The strips were sewn to gridded fusible. Pixel quilts in general with the gridded fusible stabilizer would lend themselves nicely to the cross stitch pattern.

Some quilters follow the 'big stitch' stle and use perle cotton from size 8 to 12 . At our hand quilt bees members usually buy hand quilting thread.

I have used cross stitched pieces, stabilized and then sewed fabric borders around the cross stitch and quilted. You could do that easily with your pieces and then sew together. Your work is beautiful.