so this is a simple design i made because i sometimes found it difficult to line up the magnetic field on my ender 3 pro. even the smallest misalignment resulted a bumpy contact, with an air gap between the heated platform and the magnetic bed. But not anymore!!!!

With this two small frame, there is no more misalignment!

all you got to do is to align the magnetic bed with the heated plate, and mark around the heated plate. then remove the magnetic bed, and trim around the markings, so the magnetic bed will be exactly the same size as the heated bed. but you don't have to trim all the way around the whole bed, only around the rear end of the platform. this way, when you install the brackets, the magnetic bed will snap right in between them, perfectly aligned.

just make sure to print the brackets with some heat tolerant material. i printed mine from petg, and it works fine.

sorry for the bad quality of the photos, if you have any question, don't hesitate to contact me.