Minecraft wiki entry for Creating_shapes, associated text: Set m=slope<=1. If you need a slope m>1, for example, m=8/5, use 1/m = 5/8 and instead of building horizontally, build vertical stacks of the given sequence.
Set d=degrees<=45. Similarly, if you need an angle d>45, for example d=75, consider the complementary angle 90-d=15, and do the same as above.