How to cast runes on a cloth
Scatter a handful of runes over a light cloth. Read the ones that landed face up, and leave the rest where they fell. That is the whole method, and it is the only one with an ancient description.
Where this comes from
oldest description Tacitus, Germania, chapter 10 · about AD 98
The oldest description of Germanic lot-casting. A branch cut from a fruit tree is sliced into strips, marks are scored on them, they are thrown onto a white cloth and read. Tacitus does not say the marks were runes. The earliest runic inscriptions appear roughly fifty years after he wrote this down. It is the closest thing there is to ancient rune divination, and it is not rune divination.
What the poems say
None of the four witnesses describes a way to cast or read the runes. The poems describe the letters, one by one, and stop there. What each rune means in them is gathered here, rune by rune.