It would help to know what the pattern is that you are using. Simple shapes will be super easy - ie squares and rectangles. - just add in the extra 1/2 inch. . But, if the directions call for a shape then cut multiple times , the easiest and safest way (imho) to do that would be to create a template out of paper or template material. You could cut the shape out of paper, make any diagonal cuts then redraw the shape bu adding a 1/4 inch to every side. That would give you an accurate sized block without math!!
It is that pesky Pythagoras Theory thing on those diagonal lines (the a^2 +b^2 = c^2) that will get you on those diagonal cuts - not as simple as add a half inch Here is a quick example Same 8" finished block one with 1/4" seam the other with 1/2" seam quickly shown in EQ Rotary Directions
If you get stumped - reach out - I would be happy to draw a block in EQ with the 1/2" seams for you