I Use VoxelShop 
Love it!
It can be tricky to get started with, but it works fine!
StoneVoxel were the first software I used, and it’s a smooth program but with less features.
And then there is MagicaVoxel, -I use it mostly for rendering.
But again, VoxelShop is the one I use to about 95% of the time 
Yep, that’s an Outdoor Sign Stand 