Two superb goals graced the first-half. Orient fell behind when Chelsea loanee Patrick Bamford struck on the half-hour to record his 11th goal of the season.
But 20 year-old Moses Odubajo equalised four minutes before the interval and it was old-stager Kevin Lisbie who had the final word, stabbing home a pass from strike partner Mooney in the 66th minute to extended their unbeaten run in their best-ever start to a league season.
"It's a fantastic result particularly when we've had to come from behind," Slade said.
"All three goals were well-taken, sometimes you can look at players and be critical of the way goals were conceded, but even when we fell behind, we stayed calm and the best team won on the day without doubt.
"The first menacing shot of the game gave them their lead, but from then on I thought we worked our way back into the game and showed a lot of character to get ourselves on level terms.
"Then we had two or three really good opportunities to go and get another goal just before half-time and I didn't really want the half-time whistle to come.
"It was fantastic to get the win in front of our biggest gate of the season. Moses Odubajo produced a wonderful finish for his goal and has had a real impact on the game but then, so have all my players.
"Then we had a wonderful link-up between David Mooney and Kevin Lisbie that produced our second goal, at any level, the movement and the understanding between those two to get the vital goal was terrific.
"It was only 50-50 that 'Lis' would play because he's been trying to fight off the effects of a dead-leg all week, but he's managed to get out on the pitch and stay there long enough to get us a vital goal."