I find it easier if the layers are not too thick

This is what I do.... I cut the first edge off(on the right if you are right handed)...I have the fold on a line of the cutting board. After that, I turn the board around without moving anything. I then put my ruler over the folded fabric and use only the lines on the ruler(not the mat). It comes out perfect every time...no bowing. I hope this makes sense to you. If not I will try to clearify it for you.

I,also, never starch!

I always starch and iron and "square" off the fabric.. never a problem..

first thing - don't assume that if you have the selvages lined up the fabric is squared. Hold up the fabric folded in half and move the selvages to the left and right until the fold lies straight with no wrinkles. Now the fabric is on the straight of grain. Carefully lay it down. Always cut with the fold towards you. Use the fold as your straight line. From Fons and Porter I learned, to cut the first strip a little wider and then trim it down. After that first cut, you can cut to size. Hold up the fabric and unfold - I bet you won't see the dreaded "V"

David, are you cutting a large stack? If you cut to many at one time they tend to bow like that. If so cut your stack in half and see if that helps.

David when you fold your fabric make sure the fold is tight. start your cut at the fold to selvage, the cut will be straight , if the least bit loose it will have a slight curve at the fold.

Nice illistrations Gai.

Go to Harbor Freight and buy a glass pane suction cup handle. It will help to keep your ruler from moving. Also always use rulers with a nonslip surface. You can get things to put on your ruler to keep them from slipping. I can cut very accurate strips this way. It also keeps your fingers away from the edge of the ruler so you don't slice a portion off. I learned that lesson from experience.

gal288 is right they taught us in home ec to do this only no rulers or rotary cutters had to find the thread to square fab pull it out and cut along the space in the 50s