Yeah, I'm self taught (well, books help a lot to get the idea of how to create forms). In school my teacher only was interested in modern art, if it looked like something then it wasn't any good. He always told me that fantasy art was a directionless pursuit and would lead nowhere.
That N inermis kit was the first thing I ever sculpted outside high school. The original was done in Super sculpey + premo, molded in GI-1000 silicone and cast into plastic with Monster Cast Urethane resin .
But to just have a few for a science presentation you would not have to go through those steps as sculpey can be baked hard and painted and be semi-permanent (it will eventually get brittle and start to break up after some years).
Leopardgecko: Here's a few tips to get you started:
Build your basic shape with a wad of tinfoil over a wire stand so that your trap will not have to be held while you work on it as sculpey will pick up fingerprints and indentations as it's soft and pliable not at all like toy wax which is almost like carving plastic and requires heated tools to work with. This foil core ill not only conserve sculpey but also help cook it inside and out for better hardness.
place the first layer of sculpey on the foil core and the another thin layer and stert to smooth.... Smoothing takes the longest, you'll need to smooth and smooth, when dips in the surface appear add a small pinch of flattened sculpey into the dip and smooth some more. This sucks but is an important step to achieve a professional/lifelike surface. If you're going for a more museum like bronze sculpture style "Fine art" this type is almost never smoothed and always has that "clay" look. so it's up to you to decide what you're going for.
Once you have the shape of the trap then add the details such as peristome ridges, hairs, veins, spurs, etc. using a few sponges and stiff brushes it's possible to make slight impressions and give a lifelike pored/texture to the surface after you're done smoothing Always go for the overall shape first then the details.
Sculpey should be baked and then primed with a primer spraypaint like testors or krylon before painting. I like acrylics or cell vinyls for richer cartoon charachter colors.