I have done that too when I first started.... when you buy your material it is folded in half... well fold it in half again... see that the ruler's short edge is going along the fold exactly.... then cut the edge to the right of that to get a straight line.... turn your board around without moving your fabric, then measure the width you need on the material with your ruler and cut the length you need.... I hope that makes sense.... maybe someone else can help too...... when measuring and cutting there are two straight edges that need to be exactly straight.... both of them... then there are no elbows.... good luck !!!