Hi, baking in sheet pans is okay if you need a sheet cake or you intend to carve/sculpt the cake. However, if your intention is to obtain several round or square cakes, then you will have issues with the alignment of your shapes. We are humans not machines and you simply cannot cut out a perfect 360 degrees round shape or a perfect square shape which has a perpendicular angle of 90 degrees. These factors were taken into considerations hence cake pans are made from molten metal poured into casts.
To speed up your work, increase the capacity of your oven (get a bigger 1), invest in more cake pans and a cake leveler e.g wilton brand.
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