I tried to make half triangle squares with a technique of adding 6/8 inch to the finished desired square. My finished square was still too big. Does anyone have any suggestions as to what I am doing wrong?.

Thank you,
Sally

you might be sewing too close to the diagonal line.

finished size + 7/8ths inch square
draw diagonal line on back of lightest of the two fabrics
place the two fabrics right sides together, lined up very carefully

sew 1/4" or "scant 1/4" away from each side of the diagonal line.

a scant quarter inch is really about 3/16ths of an inch. line your needle up to sew a true quarter inch, then adjust the needle position one or two clicks to the right. by using a scant instead of a true, the patch is more likely to come out the right size once the triangles are folded open.

dizzy enough yet? :lol:

as a consolation prize, consider this: too big is waaaaaaaaay better than too small because you can trim it back to the proper size. :P