So there's a painfully easy and low-resource spot for this in Minerva's Den; specifically, the gather point inside the Workshop in McClendon Robotics. As you first leave Porter's Office, you get your first opportunity to slay a Lancer and grab the Lil 'Sis. From there you can just head straight on to McClendon Robotics and the Workshop within.
First, find two Security Bots around somewhere. If you've played the DLC, you'll know that this is far from hard. But if you're still struggling, right as you enter the Workshop itself, there's a camera to your left past some water that you can use to get a couple free Bots if you let it see you. There's a shutdown right outside of there; locate it before you try this, but it's not hard at all to find. Further, there's a ton of enemies upon your first entry to this room with Security Bots.
So if you haven't been to this room yet, clear out at least the bottom floor and the turret on the upper floor. You should have the Rivet Gun from inside McClendon Robotics as well, you should have seen it as you enter. You can find a few sparse scattered Trap Rivets inside the Workshop, those'll come in handy (and upon finding them, you can buy more). And you should have found the multiple Mini Turrets before going in there as well, sitting on a set of chairs by the Ammo Store within McClendon Robotics.
Beyond setting it to Easy, I would recommend removing the "Master Protector" tonic (if you have it on) at the Gene Bank within McClendon (back towards the exit of McClendon itself, going past the Ammo Machine you should see it through the water as you head down the short stairs). Now you can do it with the Tonic on, I did, but you'll have more Splicers to deal with (The Fiery Brute often doesn't come in unless you have the Tonic on, and you have far less Spider Splicers).
Now, the final tip. Down by the gather body, you see that lit glass box? That's your hidey hole. Around back, you can crouch into it and enter. Even if any Splicers come around back, which has never happened to me, they'll be unable to hurt you.
So now for the setup itself. SAVE FIRST.
1. With your weapon of choice, destroy any lingering disabled Security Bots. They explode after a time, which could damage you or your turrets/bots.
2: With your two bots and your difficulty/tonics arranged how you'd like (obviously would recommend getting Handyman from near the camera inside the Workshop), place down all your Trap Rivets around the Gatherable body.
3: Place down your Little Sister.
4: Quickly, place your mini turrets down by the body, facing the exit door to the Workshop.
5: Hide in your safety box and watch the Splicers get destroyed.
Should you fail, just reload your save. Of course you can add any more traps you like (the main key is just the box really, feel free to experiment, but this is the most localized and easy way IMO).