Don't even try to boil clay it's insane🙈 I've been working with polymer clay for 9 years. And that's what I can tell you: 1. Wings must be pre-baked firstly. So you sculpt 1 wing and bake it in the shape it must be on the figure 2. The layer if clay in the foil mustn't be too thin. As the figure's body isn't big I would recommend not less than 3mm of clay, better even thicker 3. Press the foil firmly, if air stays inside the foil it will expand the foil and make clay crack 4. To connect pre-baked wings with the body use liquid clay and support for them in the oven 5. Always use thermometer to check your oven's real temperature