The OpenSSD project[1] might be worth a look. If you don't fancy paying thousands of dollars, you can buy SSD controller boards and raw NAND flash chips off Taobao and assemble them together. There's plenty of information on various Chinese forums (Mydigit, Upan etc.), admittedly more towards USB flash drives. Some older flash chips are TSOP rather than BGA which makes hand soldering much easier.

[1] http://www.openssd-project.org/wiki/The_OpenSSD_Project