Blender How to create a house

Below is the tutorial I am following on how to create a house using blender

Summary
1. Open a new blender project, Scale your Cube so that it is big and flat
2. On edit mode, select the top face of the cube and press 'X' to delete the face
3. On edit mode, select the bottom face of the cube and press 'P' to separate it from the others, name it "FLOOR"
4. On edit mode, select the "FLOOR" and subdivide it multiple time, now you have 100 box
5. On edit mode, you can select a few box out of 100 box to make your wall, press 'E' to bring it up to become wall