It is the EASIEST thing - I can almost promise you
I'll give you steps to make one!
1) Buy sphagnum moss (actually very cheap - from most pet stores)
2) Do you eat margerine? Yogurt? Anything in a sizeable plastic container with a lid? If not, head to the Dollar store and grab a plastic container with a lid - something large enough for your snake, but also cozy. I suggest something that is not clear, but if that's all you can find...
3) Wash said container with HOT water and dish soap, vinegar, or bleach, and RINSE thoroughly as you would with other decor/water bowls
4) Cut hole large enough for snake to fit in; either in lid or in side of container, making sure to sand down rough or sharp edges. If you do this, rinse it out again
5) Let moss soak in water (see directions) until it is absorbed. Then, ring out moss until it is damp and not wet
6) Add moss to container (with lid) and place in vive. If you want added humidity, place over or near hot spot.
TAADAA!
Make sure to check the hide every other day or couple of days for mold. If you find mold, simply throw out the moss, wash the container, and replace with new moss. I'd suggest replacing before you find mold though. I don't have an exact time frame for you, but I change mine every week or two, depending on how much time my snakes hang out in there.
Best of luck!