Note: I also didn't follow the order of the instructions from the Martha Stewart website. I did it in the order that made sense to me, and helped me figure out how the pieces were supposed to go together.
1 yard Fabric (pre-washed)
2 yards of single-fold bias tape
Step 1: Print out the pattern from the Martha Stewart website. Cut out and stick pattern pieces together. Here are the notes regarding sizing from Martha Stewart:
Use our pattern full-size for size 0 to 3 months. For bigger babies, enlarge it as follows: For 3 to 6 months, photocopy at 105 percent; 6 to 12 months, 110 percent; 12 to 18 months, 115 percent; 18 to 24 months, 120 percent; 24 to 36 months, 125 percent. If you are using a thick fabric, use the next size up.Step 2: Pin the pattern pieces to the wrong side of the fabric, and cut.
Step 8: With the wrong side of the fabric facing up, fold the bottom hem in by 3/8" twice, pin and stitch.
Sew to Speak has a great tutorial for attaching bias binding, including mitred corners here).
Step 11: Mark and sew on the buttons on the underflap of the kimono. I sewed mine on by hand. Some machines have a button-sewing function you could also use.
tutorial at MADE):