First get a template- the white one is the template and the card one includes a 1cm seam allowance.
I drew around the template in biro which I find to be the easiest and most precise marking tool. It washes out of most fabric, and anyway you only write on the back so it isn't seeable. Although it can get a bit confusing when trying to figure out how to fit the pieces on the fabric. Anyway it was a fairly simple job to sew them together (right sides together). Then I trimmed the seams and mitered the corners (snipped into the corners), then turned them the right way around. Really I've only made bunts not bunting because I haven't attached them to the string- leaving that for fussy sister.