As i am still new to knife making and dont know, what are the dangers of not having a welt? That particular sheath did not have one. Right now i am making a new one for it, that is more of a pouch type sheath.
The danger of no welt is there is nothing to protect the stitching from being cut when inserting and removing the knife. Or even if you were to take a fall while wearing it I suppose an awkward stress like that could easily push the blade right between the front and back splitting the stitches.
There are quite a few sheath tutorials floating around. Check in the top few threads in the sheathmaking section.