Connect battery holders together

[jatgm1]

So how can someone easily connect the batteries in the holder in parallel, on each battery holder, then connect three in series? (12ish volts) What kind of connector is on this and how do I wire it together properly? They just look like pins of some sort, can I order a connector for this so I don't have to solder?
If I have to solder, how am I supposed to do it without melting the plastic? I was gonna just stick a wire on each pin and connect them together or something . I assume that will be an issue heat wise. This is for a backup battery pack for a irrigation system I made with a 3 wire motorized valve and z wave relay and wiring box that I stuffed the electronics in.
I found some battery boxes that are preassembled but I wanted to figure out how to do this myself.
All the preassembled battery holders look like cheap phone chargers that might fail for any reason.
More importantly, I wanted to be able to take the batteries out without unscrewing a top piece. Here are the battery holders I'm talking about. I want to just take them out and put them all on a 16 cell battery charger/balancer I got online. Seems easier. It should last a month I think but If I charge it weekly it seems like a lvc or bms is unnecessary.

Coliao 6pcs 18650 Battery Case Holder 4 Slots X 3.7V 18650 Battery Storage Box, in Parallel Black Plastic Batteries Clip Box with Pin for DIY Parallel or Series Circuit PCB Projects https://a.co/d/7hhdxOo

**Edit**
Sorry if this seems like a stupid question but I just want advice on the most reliable efficient way to do this.

 

[jatgm1]

So, just as a thought, it seems someone in the reviews on Amazon has used a bit of wood, hot glued them onto aforementioned wood, got some like 12/14 solid Romex ground wire to connect all four cells on both sides and soldered it on, one positive one negative. I thought maybe I can do that three times and make three different packs all parallel, connected in series, and get the needed 12v for the battery, then Maybe coat it with liquid electrical tape to insulate it. Or try to leave the insulation on the wire and selectively strip little bits off and solder it then just coat the joints? I mean any advice would be appreciated by someone with more experience. But if someone finds this at least this seems to be an option.