My board was 4" x 6'. I purchased some stencils at Hobby Lobby, plus a black paint pen. I started measuring the board at 6", so it hangs 6" off the floor to avoid the base trim. In pencil first, I marked off each inch with a tape measure and added lines all the way across the board for each even foot. The inch tick marks are about 1/2" and I used a small lettering triangle I had from college drafting/interior design classes to get the marks straight. Then, I just traced over the pencil lines with a paint pen. I stained the board and lightly sanded it once the stain was dry to age it a little. I added a sawtooth hanger on the back and measure where it was to be hung on the wall. Pretty simple.
After the measurement. She's 34" at almost 22 months.
I finally finished the apron I started at a friend's craft day back in November. Matt's mom was the lucky recipient of this one for Mother's Day.