Step 6: Assembly: Unite the Cathodes!
As the title implies, this is the point where we connect all the cathodes together. Bend them over, one at a time(except for the first two, of course), and solder together. If it looks like a leg might get in the way, trim it just as much as you need to, but having extra room to solder to is nice.
Be sure not to bend too close to the solder joint, and avoid letting any contact the anodes at all costs(well, it won't be a problem until the circuit is powered; sorry for being a drama queen). We don't want shorts! Check that each LED's cathode is connected to each other's. Use a DMM's(digital multimeter) continuity mode if visibility is low. If yours doesn't have that mode, use the lowest resistance setting. Less than a few ohms is good enough to count as "continuous".
There's no need to check every pin against every other. That would be 182 checks! Just knowing that one pin is continuous with each other is good enough.
The result of this step may look ugly, but if it isn't sticking out very far, it should work fine.