In this tutorial I'll be doing movement tray for 10-man squad. I base my miniatures on 20mm washers, so the measurements will be 10cm-4cm. Firstly you'll need to cut your movement tray from cardboard or plastic.
Then add a layer of magnetic sheet.
Spray your movement tray with grey coat.
Paint your tray with TAMIYA XF-57 Buff.
Place your miniatures on movement tray.
Add some PVA glue.
Then add some sand.
After several minutes remove the excess sand.
Continue this operation until you get this result. You can add whatether flock you like.
And now you have your own magnetic movement tray!