Version One
I wanted to use up the scraps from my Triangles Sweater so I devised a repeat of the largest set of triangles for the body of the hat (8+1 with 7 repeats) with the remaining yarns (based on the amounts I have left). The brim and top is worked in the main colour.
To get the proportions correct, I used a provisional (crochet) cast on https://ysolda.com/blogs/journal/crochet-provisional-cast-on and knit the brim after. This version is slightly too tight so I unravelled it and perhaps do 6+1 with 10 repeats instead.

Version Two
I knew that I had enough materials to make the hat so for this version, I did a provisional cast on 4mm needles of 64sts and knit k2p2 ribbing for 24 rows. Then I folded the brim and joined it together.
In the following row, I switched to 4.5mm needles and I started 6+1 triangles and did increases to bring the number of stitches to 70 (k11, m1, k10, m1, k11, m1). Each triangle was 6 rows high and I knit 4 triangles. In the fifth triangle, I decreased one stitch/triangle on the third row. Then in the start of the nex row of triangles, I decreased one stitch/triangle again. I knit two more rows and then started to decrease every other row, until I had 30 stitches remaining. Then I decreased 5 sts evenly per round for the remaining five rounds. When 5 sts remained, I passed the yarn tail through the stitches and to the inside and wove in the ends.