Many are cold-forged (i.e., hammered on an anvil, at ambient temperature). The most studied ones are from Greenland, from the Cape York meteorite. For some Greenland blades, the only stock removal is the sharpening of the edge, while for others, the whole surface has been ground (distortion of the original structure shows it has been forged). There are also cold-forged telluric iron blades from Greenland.
The advantage of cold-forging compared with stock removal with no forging is that less iron is lost.
The size is limited by the size of the meteorite, but this is a limit to the volume, and the length and/or width of the final blade can exceed that of the meteorite. The largest blades I know of made this way are 50mm long, so only a quarter of the length of the blade of Tutankhamun's dagger. AFAIK, they are made from small fragments of the meteorite that fell separately, rather than pieces removed from the main pieces of the meteorite.
The Greenland telluric iron blades are smaller, since they start with smaller pieces, but, again, this is a limit to the volume.
Whether or not a meteorite can be usefully cold-forged depends on the meteorite. Some will shatter, some are too hard, and some are malleable and can be cold-forged.
For discussion of cold-forging of the Greenland meteoric iron, including modern experiments, see Buchwald and Mosdal, "Meteoritic Iron, Telluric Iron and Wrought Iron in Greenland":
https://books.google.com.au/books?id...=PA17&lpg=PA17
For the largest of the Greenland blades, see Buchwald, "Iron and Steel in Ancient Times":
https://books.google.com.au/books?id...=PA22&lpg=PA22