Seems like strange advice to not even look at the board for half of the game.
One author recommends using your opponent's turn to take stock of the position without necessarily calculating anything. For beginners perhaps this could be things like finding undefended pieces. Then on your turn you can calculate.
Early on, players haven't yet learned how to anticipate how the board state will change as pieces move, so it can cause blunders to make plans on how you are going to move before your opponent makes his/her own move.
To avoid this, early on when playing in longer time controls, don't even look at the board until it is your turn. This way you always take your opponent's move into account. Later on as you have gained more experience, you can start planning ahead while waiting for your opponent's move.