How to make octangular flower beds with landscape timber?
make a star with some string and posts, to form 8 points (4 strings crossing in the center). Then use the end points as the corners of the octagon.
Once complete, aside from a lovely flower bed, you'll be able to have UFC cage matches.
Cut the timber at 22.5 degree angles and lay the timber in an octagonal shape, then plant your flower bed.