#include paths absolute to project root in Unreal Engine C++

Inside <ProjectName>.Build.cs file add this:

public class ProjectName: ModuleRules
{
    public ProjectName(ReadOnlyTargetRules Target) : base(Target)
    {
        ...
        
        PublicIncludePaths.AddRange(
            new string[] {
                "ProjectName"
            }
        );
    }
}

Source