Up to a certain hight curving itself is not a big problem. When cutting or engraving, the laser tolerates the difference in height approx. up to 3-4 mm. If the height difference is bigger, the engraving might come out distorted and the cut might not come all the way through the material. By the way, you work with Kraftplex (wave) which is listed in our material library, and can be cut or engraved up to 6mm. 
Additionally, the height of the object itself is another limitation. The maximum object height which fits under the laser is 38mm / 1.4". We have successfully engraved easter eggs in size S. It also works for very flat bottles or various kitchen tools like cook spoon or bottle opener, etc.
Tip: If your object is rolling away, fix it to the the metal grid with masking tape, or lay foam or any other thick material around it.
