I'm not a native speaker, and I feel difficult to pronounce unaspirated stop sound properly, such as the /t/ in "let me". I found some learning materials on internet, but they are not sophisticated about the process of pronounce unaspirated stop sound. In "let me", the /t/ is unaspirated, so as materials said, I should close the mouth and block the air stream after /lɛ/, until meet /m/ in "me", then release the air stream. I don't know whether is that right or not. I'm very confused.
It might depend on what accent you're trying to emulate.
For me, Northern Br E, the 'close' is at the back of the tongue to the throat.
If I emulate a generic Southern Br E or US E it seems to be further forward, but it's still tongue, not lips.
The move to the 'm' of 'me' is a separate move.