Resin casting does not involve the use of furnaces, crucibles, or casting sand. In fact all one really needs for resin casting is a mold, some resin (of course), and time.
There are actually two forms of resin casting. The first kind is the one that more closely resembles metal casting, uses a mold and even gates and runners if it's complex enough. The second type of resin casting is simply incasing an object in the resin. An example of this is using an ice cube tray and placing an object like a small pendant in one of the tray's cavities and then filling it with the resin solution. After the resin dries you can pop it out of the tray. The pendant is now encased in hard plastic. This form is usually employed by jewelers and crafty moms but tends to be fun for everyone no matter age or experience. At the very least it's a great way to get rid of some of the clutter around your house and disguise it as art. You can cast leaves, coins, and other objects in the resin to make anything from charms to magnets.
Resin casting using mold is generally used by those who work with models and miniatures. Resin casting is a great way to make several pieces at once so you can avoid shelling out money you may not have and waiting several weeks for delivery of your items. Who has that kind of time anymore?
Like metal casting, resin casting will require you to build a mold. If you are fortunate enough then you can easily find pre-made molds, especially if you are working with miniatures. If you don't feel like buying these pre-made molds or just like doing things the hard way, then you will have to make the mold yourself. Don't worry, it's still fun.