Basically, method is the same for all 3DS. The only difference is the pinout.
This link give all the pinouts versions : http://3dbrew.org/wiki/Hardware#NAND_pinout
In your situation, here's the one you need (New 3DS XL) :
Basically, it's just to solder a 4-pins cable to the 3DS (DAT0, CMD, CLK and the ground) and the other part depend of your choice.
Some peoples sold a SD Card Reader directly to the cable, some others add a port to the 3DS, and then do a separate cable.
Here's a video :
It's for the 3DS XL but the method is the same.
And the second part :
This one talks about the dumping/writing nand part.
Thanks for that explanation.
Question 1:
There's 4 CLK points. Are all 4 points referring to the CLK? Do i get to choose any one point to solder the wire?
Question 2:
Whats the best route (least invasive) to place the female adapter? What tools do people use to cut the shell?
Question 3:
My soldering skill is a bit hit and miss. I always have problem with pointy alloy leftover when pulling off the soldering iron
How to avoid having pointy leftover when soldering at points especially with smaller points?
My technique: 1) Apply flux on board 2) Heat and apply a bit of alloy to the soldering tip and wire tip 3) solder the point
Can anyone attach some pictures of final result on N3DS XL hardmod just before shell closure. want to see the position of the wires, and female adapter. please =)