There are several ways of doing this, depending on what your motivations are…
1/ use the exact same rules, distances, unit sizes (eg 100x40 for infantry troop) but… use 10mm minis on the tray, making larger armies!
=> This is cool if you want epic games, and the option to play with your 28mm friends (even if it might look a bit weird, gameplay wise it’ll work 100%)
2/ half the distances/sizes (for 10/15mm)
=> this lets you play on a 3x2 table for standard sized games, or have epic huge battles on your standard 6x4. Some people use cm instead of " but I think it’s pointless…
3/ use existing bases from other 10/15mm gaming systems.
=> if you or your friends already have let’s say large warmaster collections, you can probably fiddle around a little bit to make these work with KoW, even if you’re not 100% at scale.
I’ve been wanting to jump into kow @10/15mm scale for a while, but need to finish some other projects first - and motivate people to join!
I think I would go with 2/, and just merge units/bases to do 1/ as well with them.