Might help to clarify what you're going for. The box construction I think you've got is "frameless" because it lacks face frames. More importantly, I'm not sure "flat panel" is what you want. Flat panel means that each door or drawer front has a frame around the outside, with a flat floating panel inside the frame. Since you're talking about very modern elements like bamboo and concrete, I suspect you want "slab" doors and drawer fronts which have no frames around them. Does this sound right?

I'm unfamiliar with "carbonized" bamboo. What sort of color are you wanting to achieve?

The horizontal grain thing is pretty limiting, especially if you have long runs of cabinetry where you want the grain from one drawer or door to flow into the one next to it. You definitely will be dealing with plywood, or perhaps veneer over MDF; horizontally oriented solid wood slabs don't play nice with hinges. If you want to DIY this, I might go for maple-veneered 3/4" MDF (a special-order item in most places) and iron-on edge tape, finished with a non-yellowing waterbase finish.

Thankyou Jon, You are absolutely right-frameless with slab fronts, couldn't think of the right names at the time. I also realized after I posted that I should have used the word product rather than wood as I think it would be tough getting solid wood horizontal grain doors. I'm open to all suggestions and the veneered MDF sounds like a good one. It's not necessary that the grain be horizontal either it's just that I want a very simple even look to the fronts. The carbonized compressed vertical stranded bamboo is absolutely stunning. The carbonization is a process they put it thru that causes some sort of reaction with the natural sugars in the plant that gives it it's darker colour so the colour goes all the way thru rather than just on the surface like a stain. It's a medium toned brown (not pale like most bamboo one sees), very little red/orange with lighter and darker striations (strands). We agonized over floor choice as we each had different ideas but when we saw this we knew it was for us. It doesn't have the "knuckles" that are so prominent in the horizontal bamboo and is extremely stable. Because of the varied striations, options for cab colour are quite open, from light to dark however I'm thinking medium(preferably) to lighter as we are in the woods and I'm afraid that a dark finish (black would be lovely-my first choice but DH won't go for it) would be too dark even though our kitchen is quite large and open to rest of house with high vaulted ceilings.
Thx again Biner
By the way we poured sample slabs of concrete this week and I am so excited. They are going to be beautiful and for first timers I'm amazed at how easy it is and how well they turned out. Can't wait to post some pictures.