The zig-zag square is:
With colour 1, chain 22, then in 2nd chain from hook:
Rows 1, 2, 3 = 21 sc, ch 1 and turn;
Row 4: Change to colour 2 and make 1sc, then repeat 5 times: 1sc one row below, 1sc 2 rows below, 1 sc one row below, 1 sc = 21 sc;
Rows 5,6,7: sc all;
Repeated rows 4-7, changing colours, until I had 4 stripes for each colour, except for last stripe of col 2 where I stopped after 2nd row. Then I made a round of 21 sc’s with 2ch in each corner per each side of the square to prepare it for joining with the daisy square.

Joining squares using: Single crochet join as you go with pull loop through (SC JAYG with PLT) video:
https://m.youtube.com/watch?v=6xL575Zf_Qc

Border
After joining the squares, for the first rnd of border I sc-ed around using a larger hook = 5.5mm and with 3 sc in each corner.
I wanted to make a “candy cane” or “barber pole” border in white and light green, inspired from this site/video tutorial:
http://www.mariasbluecrayon.com/2017/10/crochet-candy-can...
However, I changed it to:

• I used a 4mm hook for this rnd;
• I made 5 chains for each colour stripe (instead of 4ch)
• I sc-ed every other st, skipping 1 sc for each colour; this resulted in a flatter border, easier to work too; I had to make sure on my previous sc round to have / end up with an even multiple of 4 stitches, i.e. 512 sts (512:4=128 and not for instance 516:4=129 as this number would result in 2 stripes of the same colour at end of round). Border looks better this way; it’s less bulky and seats nicely, doesn’t roll either :)