Start with a perfect 5th, with either hand, then fill in a note in the middle but close to the top key than the bottom, for ex.: C E G, F# A# C#. Get comfortable with that chord, then copy it to the other hand. Now play that chord with both hands. When you can do 12 of them, each with a different key on the bottom, you have root position major chords in their simplest form, also closed.