A small piece of foil (about  2x2 inches)

Polymer clay in various colors. Some suggestions are:
Green
Brown
Black
White
Accent colors such as Blue, Yellow, Pink, or any other color that you like (optional - to make colorful marbling in the turtle's shell). I recommend choosing at least 2 accent colors if you want to do a marbled shell.

Artist Recommendations:
I recommend using Sculpey III, Sculpey Premo, Fimo, Kato, or Cernit brand polymer clay as they are easier to find. Of these, the Sculpey III brand is the least strong but soft to work with. If you are looking for sculptures to be stronger, Sculpey Premo and Fimo Professional hold up better after baking but they are less soft. Fimo and Cernit both have varieties that are softer as well, but the same applies. Kato can be more firm sometimes, and bakes at a lower temperature so it is best not to mix with other brands. These brands all come in 2 oz. bars available at stores like Michael’s or JoAnn’s, or online at Sculpey or the Polymer Clay Superstore. I have also recently tested the "Crafter's" brand by Hobby Lobby. The Crafter's Collection Craft version is similar to Sculpey III or Craftsmart. The Crafter's Collection Advanced is extremely similar to Fimo Professional. I would choose the Advanced over the Craft Collection.

Please allow time for shipping if you choose to purchase supplies online. Clay bars are typically $2 - $4 per 2 oz. per bar. You can also buy multi packs that can sometimes be cheaper. The clay will not dry out if exposed to air, so it will last a while and can be used for other projects!

**My favorite clay for softness and durability right now is Cosclay, but it is more of an investment. They come in larger, 8oz - 16oz boxes. This clay is soft to work with, but also very durable. You can find it at www.Cosclay.com or on Amazon.

The variety packs that are off branded on Amazon are sometimes okay, but they often have very soft clay that is a little tough to work with. Some kids like it that soft, but others may get frustrated with the texture as it is difficult to use to make details.

If you have any other questions about tools, materials, or colors then please send me a message.

In addition to the Outschool classroom, this class uses:
Britannica Article

Parental supervision or guidance is suggested for inexperienced or younger learners. Polymer clay should be used on a non-porous surface (a metal sheet pan covered with parchment paper, or a piece of marble, or just parchment paper laid out). Learners should avoid touching their mouth when working with polymer clay.

Parents will need to help their learner cure the sculpture by baking it in the oven after class. Place the sculpture on parchment paper or an index card on a baking sheet. Bake for 30 minutes at 275 degrees. Let it cool completely before handling.