No, not all clays for arts and crafts need to be baked. The need for baking depends on the type of clay you are using.
Traditional clay, such as ceramic clay or polymer clay, usually requires baking to harden and set the finished piece. Ceramic clay is fired in a kiln at high temperatures, while polymer clay is baked in a regular oven at a specific temperature and time.
However, if you are referring to homemade clays made out of flour or other common household ingredients, these types of clays are typically air-dried and do not require baking. They harden over time as the moisture evaporates from the clay. Homemade clays made from flour, salt, water, and other ingredients are often referred to as salt dough or air-dry clay. They are suitable for simple crafts, sculptures, or decorations.
It's important to note that homemade clays may not have the same level of durability and strength as commercially available clays like ceramic clay or polymer clay. If you're looking for a more professional finish or a clay that can withstand more wear and tear, you may want to consider using commercially available clays that require baking.