This would take some intense pre-planning. So since you obviously can't capture a black hole to launch into a trebuchet, you'd have to do it to the original star before it collapses. Then time the launch so there's enough time for the collapse to occur during travel. You'd want to back up that launch time well before "just before collapsing" as the star's surface will have expanded to just be a tad bit unruly to handle. Better to grab it before that last bit of expansion just to keep things a bit easier to handle