Daniel Sturridge put the Reds ahead in the 24th minute but they could not add to their lead and former Everton striker Victor Anichebe capitalised on Kolo Toure's mistake midway through the second half.
Albion managed to put Mel's game plan into effect much better in the second period than they had in the opening 45 minutes.
"We forget the way in the first half," said the Spaniard.
"In the second half we had a high press with (Youssouf) Mulumbu and (Claudio) Yacob behind doing good work.
"The goal came from a high press and a bad pass. This is the way, a high press together, but it is not possible when only one player does it."