Flat Bottomed Containers
ANSWER - If the canner bottom is not flat, there will not be complete contact with a flat heating element. Therefore, it will take longer for the water to heat to the proper temperature. However, since process times start when boiling or the critical pressure occurs, the proeces will still be safe. It will just take a longer time to get to the point where the clock starts. The product will be somewhat overcooked but it will be safe.