I can understand your frustration. I too was intimidated about triangles. Then one day I made up my mind I was just going to do them. I have always wanted to make a scrappy quilt using 1/2 square triangles.
And now, I am so pleased with how it is turning out. But I do it the way others have described. Cut large square, draw diagonal line, sew 1/4" from each side of line, cut on drawn line. Then trim back to size desired. And yes, I starched well before even cutting the squares.
Keep trying... you will get it. By the way, I DID sew one on ther wrong side, but after I cut it apart and looked at it, you can't even tell so I left it. Hate unsewing!
green/black scrappy triangle quilt WIP
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