You dont. At 42 inches a 4k screen is basically four perfectly aligned 21 inch HD panels. Don't think 4k for smooth fonts and "retina" style pixel density. Think of it in terms of screen real estate.
Sitting an arms-length away, I'm just imagining a lot of head movement going from the bottom (dock or taskbar) to top (menu bar or window title bar). Any tips? Maybe it works if you put only less-frequently-used windows up high.
I've used a 30" display (at arms-length), and it felt nice, but already rather tall.
I've used a 30" display (at arms-length), and it felt nice, but already rather tall.