If you don’t have a brown paper bag or prefer not to use one, you could make this recipe in a glass bowl with a microwave-safe lid or try placing a microwave-safe glass plate on top of the bowl. Just make sure you use a large enough bowl for the expanding popcorn. You will need to microwave the popcorn for about a minute longer than when using a bag.   I will say, I feel like this method does not work as well as a paper bag. It takes longer for the heat to penetrate the bowl and you’re often left with more kernels at the end.