Is nonsense asking beginners to complete a layer: once done, you lock yourself out.
The exact moment layer 1 is complete, the only rotations that do not damage your progress are U or U' (the top layer).
Tutorials forcing you into this constraint add an unnecessary level of complexity, Leaving the layers incomplete opens up an unexpected structural advantage: the whole cube can be solved with just one single algorithm.
To prove that, I built an interactive 3D site with a step-by-step guide:
