No documentation for splitting disk images into chunks

I'd like to split a raw disk image (like how it's done in `https://i.copy.sh/arch/58c2bc38.bin`) in order to not have to load the whole image into RAM, but there is no documentation on what the format of the filenames is supposed to be (all I see is just "hex number dot bin" and that does not help) and which file format I should use for splitting (I assume that I have to split the image into raw chunks). Is there any way in which you could help me?