I base all my WWII 15mm individually (except for team weapons) on steel washers, and I use them with 3d-printed magnetic sabot bases for mass movement.
http://mojobob.blogspot.com/2018/11/sabot-bases-for-15mm-infantry.html (http://mojobob.blogspot.com/2018/11/sabot-bases-for-15mm-infantry.html)
(https://4.bp.blogspot.com/-7HzPIphmHqQ/W_OrQzZd4WI/AAAAAAAAMGw/w68cQiaIqbwMMqmXaVn43EgKHjoq0TznwCLcBGAs/s1600/2018-11-20-SabotBasePrototype-003.jpg)