Weaving with 4 layers on a frame loom

My wooden frame has a nail apx. every inch. Use rag rugs or T-shirt yarn. 

Thread the frame with the first layer (black in the illustration), vertically, around the nails. Keep it loos, do not tighten it.

Thread the frame with layer 2 (purple in the illustration) horizontally. Do not interlace with the first layer.

Thread the frame with layer 3 (red in the illustration), vertically. Do not interlace with the other layers.

Take a sling of the 4th layer (white in the illustration). Weave it, horizontally, over the red ribbon but under the black. Put the loop around the nail to the right (this is not shown in the illustration). Take a new loop and start weaving again in the same way, but under the purple layer. This is how the layers are interlaced.

Loosen the weave by securing the loops with a crochet needle.