Only stack two at a time. While some quilters stack more layers, the lower two tend to shift. Shifting only a few threads will throw off your sizing. AND that is important to having accurate patches. Adding several threads across a quilt will magnify the size of the blocks. And because of bias, the enlargement is not necessarily the same around all edges of any patch. So it's more accurate to limit the number of fabric layers.

Sandy

I have never cut more than 2 layers at a time. I could not imagine getting really accurate cuts with any more.

If you are not on a firm surface you will get a "wonky" cut. I learned the hard way when I cut a "stack" on my drapery pinning table with horse hair padding..The rest of the responses are good ones also

I think the trick is a combination of good pressing, a little starch or best press, careful stacking, a nice sharp rotary blade and a good and accurate ruler (Creative Grids is just one of the brands I really like right now). I usually don't stack more than 3 layers at a time, but know ladies who bravely stack 4. I find even with a new blade you can get some skipping and wonky edges with 4 layers. ;) Good luck to you!

Two things that really helped me: Spray starch the fabric and stack them together while they are slightly damp, then press (not iron) them dry.
Whenever I want to cut several layers of fabric at one time, if I starch and stack this way, the fabric doesn't shift. And of course, be sure you have a good blade in your rotary cutter.

I have tried several layers, but always go back to only one most of the time, sometimes two. I find it more accurate. I know it takes more time, the results for me are better, even doing it that way is not a sure thing for me at times, hard as I try.

yep, big blade and no coffee before

I really love my 60 mm blade rotary cutter - It gives me more control and can cut larger stacks, but others here are right new blade and pressure are key.

i have done more than that! I use the bigger rotary cutter.

Boy are you smart! You give some of the best ideas. I look for your blue flower and when I see it comin up as I scroll down, I know that there will be a great idea to learn.