Here's how to store your samples on the same card you boot from.
On the image you put on that card, you have two partitions, BOOT and ROOT.
Get on a computer that can see and write to the ROOT partition, which uses the ext filesystem.
On the ROOT partition, edit this file:
Change this line:
SAMPLES_DIR = "/media/"
SAMPLES_DIR = "/root/SamplerBox/"
Now you can store your numbered sample folders in the root/SamplerBox/ folder
I tried to format all the extra space on my sd card as FAT32, put my samples in there, and change that line to point to this FAT32 partition on my boot SD instead, but I could not find a path that worked, maybe that partition was not mounting.
If anyone can figure that out, it would be even better, then you could add samples from any computer.
Another benefit is that the green light blinks to let you know it's loading, which is a relief with big sample sets like the Piano.