Could anyone give me advice and instruction on the best way to seam bound-off shoulders with stair steps? Thank you. 
Joining Bound-Off Shoulders with stair steps
If they’re alread bound off, I’d recommend mattress stitch. Not exactly like in the video, since the stitches are going the other way. I’d do it by putting my needle under one stitch on one side and one stitch on the other, sewing under the first full stitch after the bind off.