I buy wheat seeds from my local grain elevator and sew them in a flat plastic container...I use an underbed sweater box, but you can use a concrete mixing container (about $5 at home depot and a good size). Put some dirt in, water it down, scatter seeds liberally (when I do it, you can hardly see any dirt underneath), and put it in a warm place. Keep it moist. If you want them to sproud quicker, put plastic wrap over the top. When the seeds begin to sprout, lay a section of hardware cloth over the top, and bend under the edges so no sharp edges are showing. The grass will grow through the hardware cloth, and when it gets tall enough (I wait until it's about a foot high), you can put it in the run for your chickens to eat. THey'll eat down to the cloth, and they won't be able to pull out the seeds. It won't last long, but it's an awesome treat for them. You can just pull out the container when they've eaten it all and leave it right outside the run in the sunshine to grow back up again.
ETA: I ordered the spring mix from Sandhill just last week, and that's what I'll be using in my rotation run this summer!