Millwall cruised to a 3-0 victory over Rotherham at The Den.
Ryan Longman opened Millwall's account in the 27th minute when he cut inside and fired a wonder strike from 25 yards.
Flemming, who was left out of The Lions' starting line-up in their 3-0 defeat to Leeds on Sunday, returned and doubled his side's tally in the 58th minute.
Millwall finished off a convincing display with a Tom Bradshaw goal as he pounced on a deflected long-range strike to make it 3-0 in second-half stoppage time.
The home side started as they meant to go on thanks to an encouraging opening from Flemming.
Brooke Norton-Cuffy whipped in a dangerous ball into the box in the 15th minute, but it could only find former Millwall man Fred Onyedinma as Viktor Johansson remained untested.
Bradshaw had a promising chance in the 26th minute when the ball fell to him outside the box, but the forward struck high and wide.
Millwall found the breakthrough just a minute later as Allan Campbell found fellow loanee Longman in space on the edge of the box, who cut inside and fired a stunning strike past Johansson into the top right corner.
Rotherham struggled to string any real passes together, but managed half a chance when Sam Clucas found Onyedinma in the box, only to head wide.
Casper De Norre fired a bullet effort from 30 yards past a number of Rotherham bodies in the 40th minute, but Johannson was on hand to prevent the advantage from doubling.
otherham looked to grab an early equaliser after the break, with Onyedinma proving a threat once again when he curled the ball past Bartosz Białkowski in the 49th minute, but the flag immediately went up for offside.
Millwall's hopes of adding a second looked to have been hit by the loss of Kevin Nisbet to injury, but that did not stop Flemming from doubling their lead in the 58th minute with a punishing left-footed strike from inside the box.
The hosts continued to push for another goal to ensure a third win of the season as Norton-Cuffy had a strong right-footed effort saved from a tight angle with 10 minutes to go.
Bradshaw, who scored twice in this fixture last season, made it 3-0 in the third minute of stoppage time when the ball fell to him in the penalty area following a deflected long-range effort.