Choose some fabric for the front diffusing part of the pouch-- it doesn't have to be white! Black material can also work well as long as it's translucent. Experiment, even bring your circuit to the fabric store! Trace the perimeter of your matrix onto the fabric with a disappearing marking pen, then draw a bigger rectangle that's ~1" larger in each direction than the first, for seam allowance.
Cut out the front panel, and make a back panel that is slightly larger than the front. Fold over and iron the edges of the back panel around the raw edge of the front panel, and topstitch around three sides. Add velcro tape to the top edges and stitch the finished pouch to your bag, jacket, curtain, or any other fabric substrate you wish to adorn.