Start by cutting 2 squares (for 2 1/2" finished blocks I cut 6" squares). Draw diagonal lines in both directions.
Cut on both pencil lines and vertically and horizontally. Using a small cutting mat if you have one, makes this step easier.
Pressing half of the seams to the pink (dark) and half of the seams to the yellow (light) makes for easier sewing later.
Trim all squares to exactly 2 1/2".
A mock-up block