Sorry about the previous post - I was looking at the sleeve instructions, not the body.
I don't see chart b except as a subset of chart 1 - you work the 6 sts of chart 1a, then the 3 sts of chart 1b for 9 sts total, then repeat those same 6/3 sts across.
When you've done the 18 rows of chart 1 a/b, then you begin the 9 st, 18 rows of chart 2 and work them twice.
This note - (start Pattern 2 inside of 5 edge sts and 3 sts in stockinette st from center front edge so that the lace pattern in Pattern 2 comes between the 2 lace patterns in Pattern 1). - means you begin pattern 2 on the 9th st in from the edge which means that its lace section will end up between the lace sts from the previous rows.
Maybe CO 26 sts to try it out and see how it looks. Just do only 3 stockinette sts to begin, patt 1 a and b twice and 3 stockinette sts at the end. Do the 18 rows of that (you could actually just do 8 or 10 rows), then begin patt 2, again start after only 3 stockinette sts and do 2 repeats of that across your sts.