An FT-1 Lagun won't roll around like the Barbeque.
That class of vertical mill has great stiffness in its small footprint, so leveling as on a lathe, to "center" the flexure to a flat plane is not a consideration. It won't flex but, I believe that it's worthwhile to level it as closely as you can.
Sometimes set-ups can be simplified by using a level or inclinometer but that requires that the mill be level to start with, as a control base.
Examples might be a rough casting or a multi-piece weldment, etc. with 2 or more control points that can be relied on but are "buried" by projections.
Bridge across with a level on elevating blocks, lock part in place and cut the rough casting to establish the plane surface for all subsequent machining operations.
Easily adjustable pads a nicety for leveling and in this case, to raise my K&T mill to a more convenient level, for me.
Bob
Below the "assembled" page of my shop build guide. Yes, I talk to myself all the time, even on paper. Saves a lot of "wha'd the hell I mean by that?"
I threaded the 2" bar between chuck and live center, turned the 1" weld-pin portions, then "parted" the 4 of them on the horiz. bandsaw.
The 2 lengths of the threaded sleeves, (2.3" & 1.8") reflect approx. slab tilt. The "engineering" was established by material-on-hand.
No surprise to me, gravity has kept the 3,800 pound mill in place and the 9 sq. in. pads have not yet begun to sink in the hard concrete.