In terms of how a Sofreh is made, it is made with the same technique used to produce other kilims, although sometimes a soumak technique is used instead. The difference is in the materials that are used and the care that goes into making it because it is a religious item.
A kilim is made by stringing a warp vertically between two beams. The pattern is produced by weaving different colors of yarn in an under and over pattern, picking up the opposite threads with each alternating row. The pattern is produced by changing colors according to the design preferences of the weaver.
There are two types of joins used when changing colors. One of them produces a slit in the fabric where the colors are changed. The other uses an interlocking technique. If the slit produced is large, then it will often be stitched on the backside of the piece after it is complete.
This technique produces a firm, durable textile that is appropriate to be used as a carpet or hung on a wall like a tapestry rug. Pieces that are specifically woven to be used as a sofreh can be made as thick or thin as needed.