The short answer
Signup is three steps and asks almost nothing, then the teaching happens inside the real product rather than in a tour on top of it. Slackbot sends you a message so your first experience of the core action is a conversation you actually have, and the empty states carry the instructions instead of sitting blank, so guidance appears exactly where you are stuck. Nothing is front-loaded: tooltips and shortcuts surface later, as you touch each part. The honest weakness, which the teardowns point out, is that this only works for users curious enough to poke around, so a less motivated audience needs more hand-holding than Slack gives. Copy the empty states and the learn-by-doing, not the assumption that your users will explore.