Notice how the diphthong on “I” becomes a single vowel, though at least when I say it, it’s still fairly long. The /l/ sound and /s/ sound are made with the tongue in the same place – front of the tongue touching the top of the mouth on the ridge just behind the top teeth, but not touching the teeth. Because the position is the same, there’s no need to remove your tongue between the sounds. Just push the middle of your tongue up a little, and the /l/ will change to /s/. Don’t forget you have to stop the voicing.
This means “I strongly agree!”.