Maybe I got lucky. My flattening of the White stone took about an hour,using a used diamond stone. It was slightly out of flat,and had a fuzzy spot of ceramic that had to go. I have seen pictures of "sawn" looking ceramic stones by Spyderco(my brand),but haven't encountered one personally. I got mine in the 80's.
But,once you get the white stone flattened,you'll never have to do it again. The black one(really more like a dark brown) was perfect out of the box. Those 2 and a diamond bench stone have been the system I settled on after trying just about everything else out there. I had museum money to do quite a bit of experimenting with.
I tried water stones. They wear,are very messy,and they caused my chisels to get a slight case of brown spots,though I carefully wiped them dry. I hate to buy an expensive stone that will get worn out from use and re flattening.
For several years I used Frictionite razor stones incorrectly,but effectively,with "Lock Oil",a light weight oil that was stocked in the museum's warehouse. Not correct,but it did work just fine. I got razor sharp edges and minimal mess. The projects I have posted here were made with tools sharpened with that stone. Including the curly maple lion's head,with carved hair.
I made a knife out of D2 steel,and could not quite get it razor sharp. I honed and honed. Tried Arkansas,and everything else I could lay hands on. Then I got the Spyderco ceramic stones. Got them prepped up,and easily raised a razor sharp edge. That steel was simply too wear resistant to sharpen on any of the softer stones. There is no steel that a ceramic stone will not cut. Arkansas stones,on the other hand,grind like they were made of wood in my belt grinder. I have reshaped some broken slip stones like that. Not so with the ceramic stones! Nothing short of diamond is going to touch them!!
The only thing I ever have to do is quickly scrub off the gray haze of metal from the white stone. The black one never seems to get dirty. You can clean the gray off with cleansing powder from the kitchen. Or,give it a scrub with the diamond stone.I haven't worn out my diamond stone doing that,though I have read that some guys have. Maybe,like everything else,it's a matter of technique. Diamonds need gentle treatment. They are hard,but terribly brittle,and can be dislodged from their matrix if used with too hard down bearing. We had one in the shop that is still there after decades. It is one of the first ever made,and is a solid block of plastic 1" thick,with the perforated steel matrix on its top. It still cuts. The makers gave it to the museum to try.
I hone any nicks away with the diamond stone,then the black,then the white. I might strop a LITTLE on a piece of MDF with green buffing compound from LV. The MDF does not round over the edge like a leather strop can.
The whole process is quick and easy. I don't have to have a tub of water for my stones to sit in,or any "sharpening station" that takes up space. My cutting fluid is slightly soapy water(detergent,actually). A few drops in a plastic squeeze bottle of water. A little squirt will do. Not even enough to dribble off the edges of the stones. And,not messy enough to rust my tools.