Surgeon’s loop with an extra ( 3rd ) pass through is probably the most popular. Easy enough, just ensure everything is right when cinching it up. Another favorite is a Uni knot that is tightened and then pulled back to revel a loop. This will tighten again if you get a nice fish. It can be undone again as well. The No Slip loop knot is also in play here and produces a very strong knot. I have been using the Surgeon’s loop to get practice with it. If I suspected that during this next cast I would hook a four pounder, I would choose the Uni.

Look around a little and you might see something that would work well for you.