I sewed up Sam's first bunting when he was just a little guy. It was made out of blue and purple silk remnants from an upholstery sample book I got at SCRAP. We've added to our collection since, and we now have a nice pile of skinny spotty ones, wider double-sided ones, and the original silks. They are inside or out decorations and they tuck away flat inside a drawer or hang from a hook in the closet when I'm not using them. Loads of people make buntings to sell and give away and it's not hard to see why-- they make every day a party!
The easiest way to sew up a bunting is to decide on what sort of triangle person you are: Long? Short? Identical? Cut your fabric in strips the width that you'd like your flags to be, base to tip. Using a rotary cutter or scissors (you might make lines with a ruler and pen first), zip down your strips cutting at the angle you'd like for individual triangles. I use a rotary cutter that's designed like pinking sheers. If you're making double sided flags, layer two fabrics wrong sides together and cut through both at the same time. This is a great project for apparel weight scraps (especially lightweight ones), or make them extra special by sewing them with coordinated fat quarter packs.
To sew them together, just place your triangles (you can decide if you like them to overlap or stand wide apart) between the folds of a double folded piece of bias tape. I use a zigzag stitch, and sew a bit down off the edge into the triangle itself, to make sure everything stays put. You don't need to pin the triangles in ahead of time if you go little by little and feed the fabric into the bias tape as you go.