So i noticed this when i was crafting some items for my shop a few days ago in which i had forgotten about this.
What you will need
-A resource depends on what you craft i will craft string so i will use grass.
How this works
This is a simple thing to do to level up fast!
Step 1: Place your anvil in a realm/room that you own.
Step 2: Tap/click smith.
Step 3: Pick a recipe. (I will be crafting string because its easy to craft and i can use string to make rope so double xp).
Step 4: Select craft max, you can only craft 100 of that item at a time ,and now you've done it!
You get all the xp from the craft max so this is not like a workbench where if you did craft max for 1k string you would only get the xp as if you had crafted only 1 string. When you do it in an anvil you get all of the xp as if you had crafted 1 at a time but did it 100 at a time. (hope i explained this well enough, kind of hard to explain)
I do not know if this works with any of the new crafting station, I have not tested them yet. Their is about a 3 sec delay between using craft max. So for the 100 string i made in 3 secs i got 50xp (I'm level 25 so it will vary how much xp you get depending on your lvl) so i can make 1k xp per minute! The reason i chose string is because i can then turn string into rope and save my resources. This works with any recipe in the anvil.
Hope this helps everyone, enjoy. :D