How to fix flat surface to show typical marble texture

Hi
I’m a beginner of Blender.

I’d like to make a flat surface with marble stone texture but the flat like surface shows multiple directions of shrinking texture lines.

I guess the surface is not completely flat. But I couldn’t make it.

Hope to know if someone knows the way to make it flat or the cause of it.

Thnak you.

I think it has less to do with “the object isn’t flat”, and more to do with how you’re mapping the marble onto the object. I’ve also seen times where blender wants a paricular level of face/edge count, to properly get a clean UV line.

Sharing the file will help diag it. We don’t need the entire scene, just that piece and the texture.

I am going to guess that you don’t know UV unwrapping? If you don’t, that would be your next topic to learn. It allows controlling how a texture is applied to an object.

I could learn and fix watching video you shared!!

I appreciate it to both of you!!