After having one course of zen meditation, it seems to me meditation is pretty much the complete opposite of falling asleep. You want to stop thinking about anything, but only to feel perfectly aware of the current time and place. And your mind becomes completely focused and concentrated on.. nothing.
In particular, the part in the OP where you "picture yourself being on lake, etc" looks to me as completely anti-meditation.
Anecdotal evidence: meditating in the evening helps me fall asleep. Don’t know if it’s the breathing part or clearing my mind but it works really well 90% of the time.
The trick is that I do it laying down instead of a more conventional meditation position.
i believe it's pretty easy to fall asleep after step 1 . I suspect the uncomfortable sitting position is made to help you stay awake. In the course i took, people could even ask for someone to hit them on the shoulder with a stick, to help them keep themselves awoken.
In particular, the part in the OP where you "picture yourself being on lake, etc" looks to me as completely anti-meditation.