|Magnets are 6mm x 2mm. Grey stuff rolled up and ready.|
|Make a small putty ball for each magnet.|
|Press putty ball on to underside of base.|
|Press magnet on to putty ball.|
Hopefully that is all self-explanatory. The magnet is fixed to the base by the putty. To ensure the magnet is flush with the ground, place it loosely on the putty ball. Turn the figure right way up and gently press it down on to your cutting board (or any other non-magnetic flat surface). The magnet will squish up into the putty, ensuring it is a) stuck to the base and b) perfectly flat and flush with the ground. When the putty is set, the figure can be placed into the tray.
Very light figures such as these and plastics will hold pretty well with these small magnets. Cavalry figures might need two to hold. Metal figures are a little heavier and might need two or more. Bigger magnets might be needed for really heavy figures, but do bear in mind that the depth of 2mm is about right for a standard slottabase. Anything deeper than this will be deeper than the recess under the base and thus it will not be possible to stand flush with the ground.