If I am correct to make a private key you have to first generate a random 256 bit number then transform it to a WIF private key using base 58 check encode, does the mnemonic phrase is generated from this WIF private key or is there a step in between ?

I am using this guide http://www.righto.com/2014/02/bitcoins-hard-way-using-raw-bitcoin.html so maybe it is outdated