Hi guys, I just got naniwa 1k and a 3k/8k combo stone, need to lap them flat, I picked up a King lapping stone for 20 bucks but it feels reallly course and doesnt feel that flat so I'm not too keen on using it, I bought a black glass board which seems pretty flat to use the 320 grit wet/dry sandpaper on, but when I did that method afterwards when honing it seems the stone isn't flat still, should I draw antoher pencil grid and re do it ? can someone explain the method to me in detail in case i'm missing something?

I'm getting a Dmt diasharp but the store near me can't find the ones they were meant to have in stock so now I've ordered one it's coming soon. but I really want to start learning to hone asap