This can be done fairly early on and pretty much in the same area as the 'Blast Radius' achievement. Once you've thrown the grenade, walk around the corner and you'll see more Swarm CELL and there should be more than enough of them to kill.
To slide you need to first sprint by pressing and holding in then while sprinting hold down to slide for a period of time. What gun you use doesn't matter, though some on certain targets are better, like the shotgun. I simply just kept sliding in this corridor with my assault rifle and killed all the Swarm CELL and the achievement unlocked!
I just got the achievement. I recommend doing it on Level 3 (that is counting the prologue level. It's when you go down into the subway you will encounter a bunch of alien like bugs. As far as I know they didn't attack me. So slide by sprinting with LS and clicking B then while sliding hold in RS to do a melee kick. You'll kill these bugs instantly. Just do it on 5 of them and you get the achievement.
And no it doesn't have to be in one slide. I think that would be impossible.
Actually I should clarify, I just looked at the level select and the level is "Second Chance 02." It's weird how the levels are in this game. i assumed they were after a transition and an achievement but it seems that's not the case.
I recommend doing this on Dark Hart level, when you are underground you will find some kind of creeps that eats out of a soldier (Small one with a red light on it's back), you might find them earlier but if you are going for the Hole In One, you could do them both easly. What you do is just sprint and slide on them, no need to shoot/melee.