Thanks for asking the question of how to bake biscuits without burning them on the bottom. I assume you're cooking biscuits from the can. If this is the case it can be one of two things.
First it sounds like your oven is not cooking at the proper temperature. I recommend using an oven thermometer to see if your oven is heating higher than what's indicated on your temperature reading. If this is the case make the adjustment down to the proper temperature and try baking the biscuits according to the package directions.
Second, your problem could lie in the pan you are using. Try using a baking/cookie sheet that's designed for biscuits and cookies, this might work as well.
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