Mel was appointed as head coach in January as Steve Clarke's replacement and was tasked with keeping the club in the Premier League following nearly four years with Real Betis.
The Spaniard was able to achieve that objective, narrowly guiding the Midlands club to safety as they finished the season just three points above the relegation zone in 17th.
However, the 51-year-old was able to engineer just three wins from 17 Premier League matches in charge, and left the club by mutual consent on Monday.
"I said at the start of the season it would be really tight and go down to the wire – and it proved that way," Morrison told the club's official website. “But we stayed up.
"We need stability now, to bring in a few players and get the togetherness again.
"West Brom is all about hard work and I think we got away from that a little bit.
"We maybe got complacent; four years in the Premier League, having previously finished 11th, 10th and eighth, is a big achievement for this club.
"This season has been a bit of a reality check and I think it will be good for us going forward."
Tim Sherwood and Malky Mackay are among the favourites to take over at The Hawthorns.
