Magnetron from a scrapped microwave oven
Scrap steel plate - mine was an off cut of the 150x50mm that i cut a 100mm square from (3mm thick)
Scrap piece of reinforcement rod or a bolt
Welder - MIG in my case but a stick would work fine.
Angle grinder with a cutoff, a “flap” disc, and a grinding disc
Step 1: Magnets
Step 2: Steel Preparation & Welding
The plate is galvanized. If you are not aware of the issues with gal then probably best to to a bit of research for yourself. What I did was use the flap disc to clean the gal off both sides of the plate. Also when welding set up a fan to move any fumes away from you. And finally weld in an open, naturally ventilated area.
Stand the rod using a welding magnet and tack on opposite sides. Remove the magnet and complete the weld. I then ground the weld back to ensure the magnets were able to sit flush at the bottom. Mark the edge around the magnet. Remove the excess with the cut off disc on the grinder.