How to have a clean flat surface after boolean modifier for adding materials I've got a cylinder that I've cut up into different sections from using a boolean modifier, when I go into edit mode to add my textures/ UV images onto the surfaces I have lines/ edges going across the surfaces. 

So if I try getting rid of them it affects the surface of the shape and then it is no longer flat, it completely morphs the shape. Is there any way of going about this differently?
You can select some or all faces, then X > Limited Dissolve, to make ngons, so that flat surfaces will get merged/simplified.



Additional options such as Max Angle can be set by pressing F6.