That's entirely up to the slicer you use. What you're referring to is called a raft. By default the software that Utlimaker provides (cura) does not create a raft. Other slicers like KISSlicer and slic3r also allows you to enable/disable the raft as you see fit.
Most ultimaker users use a slicer program called "Cura" which is open source and is actively developed by Ultimaker staff. The feature you refer to is called a "raft" in Cura.
I have never used that feature. I print directly on the blue tape (on UM original) or glass (on UM2).
In my opinion the raft is just an excuse for people too lazy to properly level the print bed. And on the UM2 it is very easy to level and I only had to level a month ago and it hasn't needed any levelling adjustment since then.
On my UM Original I have to re-level every day. It kind of sucks.
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