Extract a piece of work from the project the new hire will be working on. Set up scaffolding and any boilerplate so that only have to implement one new feature (or fix one bug). Give it to another employee or yourself and solve it while recording how long it took. If someone that's familiar with the project took 4 hours, simplify. If someone that's unfamiliar with the project took 1-2 hours to solve, send it out to candidates.
If you can't do any of the above, you might have process issues that you need to solve prior to getting a new hire in the first place.
Oh, and if the take-home exercise is expected to take 4+ hours, pay the candidates to do the exercise.
Extract a piece of work from the project the new hire will be working on. Set up scaffolding and any boilerplate so that only have to implement one new feature (or fix one bug). Give it to another employee or yourself and solve it while recording how long it took. If someone that's familiar with the project took 4 hours, simplify. If someone that's unfamiliar with the project took 1-2 hours to solve, send it out to candidates.
If you can't do any of the above, you might have process issues that you need to solve prior to getting a new hire in the first place.
Oh, and if the take-home exercise is expected to take 4+ hours, pay the candidates to do the exercise.