With no rules, but inspired by literature written in the past and now and experimenting for 10 years, I have come to the conclusion, that if you are doing all the processes yourself, or with very little assistance, the simplest way is to ROOT RET THE STEMS and COTTONIZE THE FIBRES.

You may not get fibres quite as fine as if you dew or water ret, but, the fact that you donít have to handle the nettles while they sting, or while they are rotting and smelling, not to mention the use of water and the pollution of the waste water makes producing the fibre in this way worthwhile.
As a bonus the waste straw also has many uses.