Prebuy or repurpose a container. This one is from Ben Franklin Crafts. Used 40% off coupon and paid 3.50 for it. Buy some small sprigs. You can get these at Wal-Mart for a $1.00 each. I used six. Also, get some green floral foam for $2.00.
Cut the green floral foam to the size and shape of your container. Hot glue in place.
Cut the stems off of the flowers. Starting on the center of container work your way out. The trick is to put a center one in and then put a square around the center (about a third of the way to the edge.) Then do a diamond around the square (about 2/3 of the way to the edge). Then place sprigs at corners of container.