I eyeballed the size and shape I was after and began by cutting a fabric piece 4 1/2" wide by 6" tall. To create the tumbler, I found it worked well to place the rectangle exactly in the lower corner of the cutting mat along the axes and at the zero mark.

Place your acrylic ruler at the very top left corner so it also crosses the 1" mark on your cutting board. Cut along the ruler, trimming the left side off; discard. Similarly, place your ruler at the very top right corner so it also crosses the 3.5" mark on your cutting board. Cut along the ruler, trimming the right side off; discard.

Here's your tumbler block! See how easy that is? And if you'd like your tumbler shaped or sized differently than mine, just adjust your beginning rectangle.

Once you have your block design set, you can layer up your fabrics, cut multiples at a time, and start sewing!