Polymer clay is not picky; it will cure equally well in a regular kitchen oven, a convection oven, or a toaster oven, though it does best in an oven with a consistent temperature. Small toaster ovens may not be as consistent as larger ovens. Sometimes the heating element has to kick on and off to maintain the temperature. This can cause heat spikes that exceed your set temperature and may result in burnt clay. However, many artists and hobbyists find that toaster ovens are just right for their needs. It's a personal choice.
Manufacturers warn that polymer clay shouldn't be cured in microwave ovens, but some clayers have run experiments with boiling polymer clay both on a conventional stovetop and in microwave ovens. It is important to note that you should never try to cure polymer clay in a microwave oven or on a stovetop without submerging the clay in water. Doing so will cause it to heat unevenly, burn, and release harmful gases. While it is possible to cure polymer clay with a microwave or on a stovetop (see related links below), regular ovens and toaster ovens remain the most common tools for curing polymer clay.
When deciding how to cure polymer clay, remember to consider these safety concerns.