The major reason that papyrus works to make paper is that the inner stems have a slightly gummy substance ( a kind of starch)that effectively glues the strips together. The inner stems are stripped out of the reeds, soaked in water, and then sliced finely. The slices are laid side by side closely together, then another layer is made but with the slices laid at right angles to the first. They are allowed to set a little and then while still damp, they are beaten until the fibres are flattened and compressed together. Generally the sheet almost doubles in size as it's beaten. The finished sheet is laid under a heavy weight until dry. Then it is rubbed with a round stone until the surface is fine and smooth and ready for use.
A very crude version can be made by just slicing the inner stem and laying it out as before and then simply compressing it for a while.
To use nettles or cotton or linen is really more a papier maché process.
The simplest 'paper', and it's good, and it lasts very well, from native plants, in this country, is made from the inner layers of birch bark.
The inner pith of the native river rush, schonoplectus lacustris can be used almost like papyrus. It's not as big, or quite as sound and it's a bit less securely bound, but it's interesting to have a go
cheers,
Toddy