I find Sam Harris' Waking Up guided meditation lessons the most useful (can find it on mobile app stores, the 30+ lessons are free and start off short and simple).

Until those, I thought meditation was inherently coupled with eastern mystic bullshit with zero benefits for anyone who didn't want to buy into a bunch of other baggage.

He has a book by the same name as the mobile app. The first chapter (read out loud here) is what first started convincing me that mindfulness was something I should seek out and develop: https://samharris.org/podcasts/chapter-one/

I started doing it while laying in bed before falling asleep. Ended up with a daily morning practice sitting up on my bench.