This blanket is modulated - made using an ‘outside in’ technique where each square is knit directly onto the last rather than assembled later. I started out using DPNS, but changed to a circular needle.Whatever method you’re most comfortable with is fine.

For my starting square, I cast on 64 stitches in black (double stranded), evenly spread over four DPNs or a circular needle (magic loop technique), then joined in the round.
Row 1: Still in black - SSK, K12, K2tog four times. Cut black yarn, attach coloured yarn (double stranded).
Row 2: Now chosen colours - Knit
Row 3: SSK, K10, K2tog four times

and so on, repeating last two rows, the K stitches decreasing by two every second row, until

Row whatever: SSK, K2tog four times - (8)
Last row: Sl 1, K1, PSSO four times - (4)

Cut yarn, draw yarn through four stitches, pull tight, and draw end through to back. I tend to use a crochet hook, because it’s easier.

The second square is exactly the same, only the last sixteen stitches of cast on are picked up and knit from an edge of the first square. I also use a crochet hook for this bit, lining the picked up loops of yarn up along the handle and then just slipping them off the bottom end of the hook onto my needles when I have sixteen. (This won’t work if you have a crochet hook with a moulded handle.)