I use a chair for formal practice. Lotus and even half lotus is too harsh on my right knee. When I was pursuing lucid dreaming the last two practices while lying in bed just before sleep was five or ten minutes of mindfulness of breathe followed by a silent mantra to set the intention to become lucid and that would send me off to sleep.

Informal practice is any position engaged in any activity at any time with any technique including no technique. I suppose if one can always be meditative without any technique one is there. When everything, both external and internal including sense of 'I am", is but a seamless series of forms arising and subsiding in the field of awareness.

That last part is true non-dual awareness. The awareness even the observer is merely a passing form in the field of awareness. Escaping the observer trap.