You want to cut soap when it's at the right texture, not by time. If you make the same (or similar) recipe a lot, you'll get a feel for the amount of time it takes to get to the right texture. But when doing a first-time recipe, what works for your other recipes might not work for this one.
I want to cut my soap when it feels firm but still yields slightly to gentle pressure without denting. It will feel like refrigerator-cold mild cheddar cheese or colby cheese. If you have some of this cheese in the refrigerator, you can calibrate your fingers by pressing on the cheese.
I do not want the soap to feel like aged cheddar or Parmesan (too hard, too brittle) and I don't want it to feel like cold cream cheese either (too soft).
A soap high in tallow can become brittle and hard to cut early on -- a lot like a soap high in coconut oil -- so start testing early so you can cut it before it's rock hard. It's been awhile since I made a soap like this, but I'd start checking about 6 hours and see if it's ready. It might be or it might not depending on the other fats in the recipe.
A soap high in lard generally isn't a brittle soap in my experience and is able to be cut over a longer time compared with high tallow and high coconut soaps. My high-lard soaps are often ready to cut at 12-24 hours, but are still pliable enough so they can be cut for several days after they have been made. I sometimes split a normal sized bath bar into half to make samples, and I often make samples like this some days after the original bars have been cut.