For my F, I used a medium-sized chunk of l-fabric, sewn to a skinny b-fabric, sewn to a skinny l-fabric, sewn to a wide background. I did make a couple of slices along the left side and the top to get more of an angle on this one. For the E, I started in the middle, cuz I like having that middle section be shorter than the other two legs, then added from there.
And here they are are finished. The F has more of a straight bottom than you can tell from this photo, tho the right side does angle.