The so-called base that came with my new Buffalo WZR-600DHP router was a complete joke. It wouldn't actually attach in any way and the router was tilted and more likely to fall over if you tried to put it on the base than if you just left it off the base. So I scanned in the bottom of the router, picked off dimensions with gimp, and whipped out a base in openscad that actually supports the router and makes it quite difficult to knock over.
Just print, and push on bottom of router. It stays on nicely with just a friction fit.