The even surface tip is so important! I'm glad you brought it up. This was a problem for me for quite a while - until it dawned on me that my cutting surface was not flat. I fixed that problem and my cutting has improved.
The other thing I do that improved my cutting of strips - Assuming that you cut across the width of fabric, folded once selvage to selvage, press a sharp crease into the fold. That seems to minimize the curving at the center when I cut.
Lastly, I have learned the hard way that cutting through more than 2 layers of fabric - more than one single selvage to selvage fold - creates uneven cuts and curving. Maybe others can do more than 2 layers at once, but it just doesn't work for me.
The other thing that greatly improved my cutting was to spray baste the bottom of the ruler I use for cutting. The ruler clings to the fabric, so the ruler doesn't slip out of place while I am cutting. Note that I had to rub some of the spray baste off of the back of the ruler immediately after spraying. In some places it was too thick on the ruler. If you don't like the spray basting on your ruler, it can be washed off, but it takes a bit of elbow grease, soap and water or a vinegar/water solution.
Last edited by cathyvv; 05-19-2015 at 08:11 PM.