Place a triangle on a square (by eye) as shown above. Sew a 1/4" seam along the long edge.
Press open.
Trim, as shown above. No need to trim off the tan fabric under the triangle.
(Unless you plan to hand-quilt.
You can't miss getting sharp points with this method.
And even if all your triangles aren't exactly the same size
(since you position them "by eye") so what? Who cares?
I think slight variations add a charming vibe.
You could spend the next 100 years making awesome quilts with just this trick!