It is odd to say "About one worker". It would be normal to say "About 100 workers", to mean between 90 and 110 (or more, or less, in context)

If you mean a small but non-specific number use "a few":

The company employs a few contract workers.

"a few" could mean "one" or "zero" but you can explictly include "zero" by saying "... sometimes employs a few contract workers."

It would be fine to say "about 1 metre" which I would understand to be in the range 0.9—1.1 cm (or perhaps a smaller or larger range, in context). But I would not call 2m to be "about 1m". Similarly, I would not call "2 workers" to be "about 1 worker". This makes "about 1 worker" a rather odd expression.

Similarly "about fifty to a hundred workers" is fine, but "about one or two" is odd. Just use "a few" in this situation.

It is odd to say "About one worker". It would be normal to say "About 100 workers", to mean between 90 and 110 (or more, or less, in context)

If you mean a small but non-specific number use "a few":

The company employs a few contract workers.

It would be fine to say "about 1 metre" which I would understand to be in the range 0.9—1.1 m (or perhaps a smaller or larger range, in context). But I would not call 2m to be "about 1m". Similarly, I would not call "2 workers" to be "about 1 worker". This makes "about 1 worker" a rather odd expression.

Similarly "about fifty to a hundred workers" is fine, but "about one or two" is odd. Just use "a few" in this situation.