Procedurally created cube has flat shading / lighting and I don't know why

Hi everybody.

I have a problem: I am trying to create a cube procedurally via the Procedural Mesh Component. The generation itself is working, but the problem is that my cube is totally flat-shaded and I really do not know one, though I suspect it has something todo with the UVs or normals of my mesh section. As you can see in the images, I have 8 vertices arranged to form the cube and I draw triangles between them all fine so far. But I really do not understand how to assign the UV coordinates to these 8 vertices correctly.

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These are the normals which I am using, all pointing from the respective corner directly outwards:

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What I already tried was treating them as 2 seperate squares (bottom and top) and have them arranged between (0,0) and (1,1) like this:
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But that just leads to the flat shaded outcome. Same happens for all (0,0) and all (1,1).

When I try to let the system calculate the normals and tangents like this:

The outcome looks totally weird:


The problem is I do now about the usual Cube UV splitting thingy but I do not know how this applicable here. Because I only have 8 vertices and I cannot “split a vertex in half” so I do not know where on this uv system my vertices should lie. For example the right side of my cube is vertices (0,1,4,5) so I have don’t know where on my UV scale vertex 0 should lie, in the top right corner for the bottom face, or in the bottom left corner for the right side.

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Because this is my current arrangement for the UV space:


And I have no clue how and where the side faces lie in this. Can anybody help me with this?