Wonton wrappers vary in thickness. Often the crab rangoon will hold their shape on a regular baking sheet without any support. If you find that the corners are flopping over, you can put them in a mini muffin tin that has been lightly sprayed with nonstick cooking spray (see photos in post above). This will help them hold their shape while baking.
I've often been asked if these can be made ahead. The crab rangoon can be formed and refrigerated up to a day ahead. Cover them with foil or plastic wrap to prevent them from drying out. I do not recommend baking ahead as they do not hold their shape and crunch for more than an hour or so and are best served warm.