Tack you skin to a board while wet. I use a staple gun, putting staples through the belly scales and stretching as I go. You don't want to salt or borax the skin, it is not necessary and makes a skin very hard to glue on unless it is rinsed a zillion times.
Use a spoon to scrape the flesh from the center to the edge of the skin, get it all.
After a few days, use a pair of scissors to cut the skin loose from the board. Cut at the line between the belly scales and back scales.
Roll your dried skin up and store in a Ziploc bag.