I have magnet based all of my French ironclads using self adhesive magnetised strip bought from Poundland, for a pound a roll surprisingly enough, which is a bargain by any standards. There’s enough on a single roll to base a whole fleet of ships and it’s a convenient 19mm in width, so a perfect fit for my 20mm wide laser cut mdf bases. 

Here’s how I do it and it’s very, very quick:

1. Cut a length slightly longer than required with a sharp blade and ruler, using a spare base as a template.

2. Unpeel the backing paper and stick the magnet strip to the base, leaving a bit of an overhang at both ends.

3. Invert the model and slice off the excess at either end with a sharp craft knife, using the edge of the base as a line on which to cut.

The tape itself isn’t that strong but it’s more than enough to take the weight of a 1/2400th scale model ship. You can stick them to the side of your fridge and they don’t fall off, which means that a metal sheet lined RUB box or metal tin is an ideal storage option. Not bad for a quid! You can find the tape in Poundland but it’s not always there, so worth looking out.