Should I lightly boil or steam meat (eg, beef) before searing

One potential downside to this method is that with a thick coat of flour, you're mostly browning the flour, not the meat, and thus possibly creating different flavor compounds than if you were searing the meat directly. Maillard reactions are complicated stuff. If you're doing this, you should probably shake off excess flour to leave a very thin layer so that you still get browning on the meat itself.

The related problem is that you're less able to accurately measure the amount of flour, less able to make sure it's easily browned, and thus less able to control the overall balance of thickening power and flavor it contributes. Roux (flour cooked in oil as a base for sauces) gains additional flavor, but loses some of its thickening ability as it cooks. You could monitor this over the surface of your meat, but that goes against the typical wisdom of not moving meat around the pan as it browns - that is, you can't see how browned the floury surface is getting when it's face-down.

Personally, I'd prefer tighter control over both of these processes over the convenience gained by browning the meat and flour together. You can easily brown the meat, remove it from the pan, then add the flour and some additional oil to create a separate roux without losing much time. A slurry will work too, but takes plenty of cooking before it loses its raw, grainy flavor.

"For the same time" seems to be your problem here. An oven will warm a pot much more slowly than a stovetop, especially a heavy iron stew pot. You'll need to monitor your temperature, and only count the time after it reaches 68 Celsius. The warming up phase can be easily close to an hour in the stove, eating away a lot of the actual cooking time.