Cut all your wires to about 3" -- this will ensure you've got enough wiggle room to get everything situated in the shell but not have excess wire hanging around.

Stranded (flexible) wire will work best since you may need to flex the components around a bit to get them situated in the seashell.

On the neopixel ring, it's easiest to stick the wire in from the front and solder on the back to ensure you don't melt the LEDs or break anything.

Notice that there are two wires going to Flora's GND pad, so it will work best to twist them together at the ends and solder them in at the same time.