The O's went into the game on the back of an eight-match winning streak.
But they only had a Kevin Lisbie penalty to show for their efforts as the Iron ran out surprise 3-1 winners.
However, Slade takes his side to Notts County next weekend determined to get back to winning ways.
"We didn't perform as well as we would have liked and we have to bounce back," said Slade. "We were under par, it's as simple as that.
"But we've got a week to get over any knocks and bruises we've got, and we'll still go to Notts County in confident mood."