This is really cool: > Securely erasing saved keys is just as important as generating them. It’s especially challenging to do so on flash storage, where wear-leveling might mean multiple copies of data need to be erased. To address this issue, iOS devices include a feature dedicated to secure data erasure called Effaceable Storage. This feature accesses the underlying storage technology (for example, NAND) to directl…
What purpose do you want to access raw NAND? If you are okay with just a basic low speed connection to read the NAND, there is a fairly standardized async protocol which you could achieve with a dozen GPIO pins. You could also use a FPGA or and NAND flash programmer (like of like the old EPROM programmers)
However beyond this, you need to know a bit more information to interpret this raw data. This includes any data framing structure, error correction, scrambling, encryption and read error recovery algorithms. A lot of this information is non-standard or only available under NDA from the manufacturer.