Ive done it before with shock cord/paracord (i prefer shock cord with this method), malice clips, velcro strap keepers or web management keepers, and a 90 degree adapter.
The vecro strap keepers work the best and weigh next to nothing. The ones kifaru uses are pretty rigid and wide. Ill show some pics at the bottom. The smaller you make the loop the better. But any kind of velcro that has hook on one side and velcro on the other will work. Velcro cable ties, hook and loop fastener rolls, etc. Put one on every other molle loop and its just as secure as running it the way it was designed.
Hard to say how Id do it without knowing how many rows wide and long youre trying to attach.
This is a pretty simply 3d printed adapter though, might work: