Kydex can be molded in many different ways. A Foam press is the easiest way for DIY. If you buy 4x8 sheets of kydex you can save a few bucks per square foot, but then the freight will get you if you only buy one or two sheets. If you can get it for less than $4 psf buy it asap. Plastic is going to go up in price very soon.
I use a cookie sheet and place the kydex in the oven for a few minutes at 350. It does start to smell so having a good range hood is a must. Be sure that you place the unfinished side facing down. The side with the texture will start to stick and stretch as you try to remove it. If you are molding small items, a heat gun could do it, but you must keep moving it around so that it doesn't blister or burn the kydex. I use a heat gun for extra bends or to remove tightness around the mold.
My press is sold at knifekits.com as well as other knife kit websites. However, as long as you can get the kydex into the press before it starts to cool off too much, it doesn't matter what press you use so long as it’s rigid and the foam is able to flex around the mold. I have noted that its better to cut off more kydex than needed for the mold since things don't stay in place all the time. Also, Quick clamps works really well for foam presses.
You can cut it by scoring one side with a box knife, and then bend and break through. I score the side with the finish and allow the unfinished side to break. A good square and some quick clamps will aid you while cutting. After your done molding, it best to rivet it together before you start cutting off any extra. Keep whatever you molded inserted while you mark the holes for the rivets. A drill press is a great idea. There are also drill bits that knife kit sites sell that are great for drilling kydex, but any good bit will get the job done.
A belt sander is next on my “to get list.” In fact, I am planning on getting one later today. So that I can finish some kydex molds.
You’re going to have to just play around for a while, and you'll start to think of better ways. Molding Kydex is like working with a puzzle.