Although the pipe flexes to a degree, it's not "floppy" as such. It's a bit like the outer sleeve of a bike brake cable if you know what I mean (coiled steel coated in plastic/rubber). You just push it down the dipstick tube until it hits the bottom of the sump.
Like Nic says, you might end up with an egg-cup full or so of oil left, but in the scheme of 4-5 litres of oil it's nothing (there'll be more than that stuck around the nooks & crannies of the engine anyway).