Here’s how to bake polymer clay: 1.Preheat the oven to 225°. 2.Cover a baking sheet with parchment paper. Place your clay pieces on the baking sheet, leaving space between them. Cover your tray with aluminum foil to prevent any discolouration. 3.Put them in the oven and bake them for approximately 20 to 25 minutes. Make sure to check your oven every 2 minutes and ensure that your clay does not burn. If your clay feels a little gummy when it's hot but still holds its shape, they are baked properly. 4.Once you have baked them, take the baking sheet out and let them cool for an hour or two.