No offense, but if you didn't know how to do this, how did you end up responsible for this?

No offense taken - I've wondered that myself lol - I'm using a build on your lot builder who will do all the connections once I get to the house. I had a contractor lined up to do all the trenching, etc, but they did a terrible job on the driveway so I'm not having them do anymore work, but die to time crunch haven't been able to line up another contractor. Worst case scenario the builder will do it, but that will cause delays and $$ that I'm trying to avoid if possible.

Typically, as soon as the foundation is built and braced or the first floor is on, it's backfilled for the safety of the trades on-site. When it comes time to install drains and the water line, which often run together, the backhoe digs and backfills again. No big deal, no placeholders needed.

BTW, that seems a problematic place to run a water line, where it may be vulnerable to backfilling damage and frost if you're in a cold or very cold climate.

In any case, check with whomever brings in the supply what their procedure is, listen and follow it.

This is appears to be a PVC sleeve through foundation that suppose to be two pipe sizes larger. You can fill the sleeve with silicone or tar like stuff, maybe roofing cement, to seal the gap between the sleeve and the water pipe. Ideally you want it at the same depth as a trench. Are you on well or city water [where you will need to install the meter]? I assuming well, you need 1" black poly NSF rated. Poly is flexible and difference in depth is not an issue. Connection could be done at the time of trenching [later].

Dig the trenches and place all lines prior to backfilling.