One of the first things I noticed with libre was that I'll easily go from 5 to 9 or 10 within a few hours of getting up, the so called foot-on-floor, so I learned how to pin it with a unit or two, so I'd be sailing into lunch quite happily on an an even 5 instead of dragging it back down from 9 with a meal correction.
Bolusing without food goes against all the DAFNE rules, but docs are admitting that now that cgm is slowly becoming more prevalent, they're seeing things they simply weren't aware of before, so they're becoming more willing to accept "creative" insulin techniques.
An additional side effect of a 2u foot on floor pin is that if you're having brunch, say, 90 mins to 2 hrs later, that 2u will be heavily into its action path, and some of it, according to Dana Lewis, may have actually reached the liver, which does the heavy duty spike buffering in non-T1s (80% of natural insulin goes to the liver for that purpose), so having different layers of stacked insulin at different points in their activity, say, 2u 90 mins and then say 8u 20 mins before, can be hugely effective in avoiding spikes.