You would spot drill, drill the web size of your 1" drill, then 1" drill to depth. Now that we know the actual purpose, just stop at the 1" drill. This allows a less-than-rigid machine to cut a large hole with the least groaning and grindin' noises.
Since we're dealing with a machine that'll be about as rigid as a well-done spaghetti noodle, and as the original question was how to get a flat-bottomed hole, after drilling to remove as much material as possible with the cheap, easily resharpenable tool, then use the 1" end mill to get the flat bottomed hole. But a 1" end mill will require a LOT more rigidity than the drill bit, as it's not self-centering. Think about using a 1" end mill in a drill press-it isn't likely to come out good. So, we need to lessen the rigidity needed, and the power required to cut, by removing one cutting face-you'd grind the end of the flute back so that only one side of the end mill is cutting-now you've got an accurately sized 1" boring tool without going to the expense of a full boring head, that you couldn't make full use of due to the machine not being up to it.
Also you could use an already broken end mill to do the job and save some cash and a broken tool from the scrap bin.