After the Welcome Amiibo update, villagers will not place their houses on patterns as long as there is another open space for them to go. I used this trick to move all of my villagers into the exact locations I wanted. It took a lot of planning and I had to make a few adjustments after learning that some of the plots I set up weren't viable, but in the end I was really happy with the result.
1. Select a 3x3 plot of land where you would like a villager house to go. Make sure there is enough room on all sides so the plot doesn't touch any cliffs, rivers, rocks, PWPs, or other buildings. There are guides online that go into more detail about exactly how much space you need so I won't go into all the specifics here.
2. Place patterns surrounding your chosen 3x3 plot of land. You can leave a space open for the door or not. It shouldn't matter, but I always left the space because it helped me visualize things better. This is what it should look like after you're done. Note: Not my image.
3. Repeat step 2 until you have as many 3x3 plots as you need. If you leave them all open, the villager should move into one at random. If you want the villager to move into a specific plot but you have multiples laid out, place a pattern in the middle of every plot where you
don't want that villager to move, leaving only one open.
4. Place patterns throughout the rest of your town, making sure that no 3x3 areas are left open except for the ones you made. This can be the tricky part because trees, bushes, flowers, and such can alter your perception and make you think you covered a spot when you didn't. Villagers will move on top of all these things, so you have to be extra careful. I tried to place patterns every two spaces to make sure everything was covered. I would move flowers out of the way if necessary. If trees or bushes were in my way, I just placed extra patterns around them to be safe.
5. Not required but highly recommended! On the day you expect a villager plot to appear, log in using a new save file first before logging on with any existing character. Check your town to be sure the villager plot is where you want it. This is where you'll find out if you missed a spot while placing patterns or if the plot you created isn't going to work. If everything looks good, you can save and delete the new character. If it's not good, you can quit without saving, time travel back to the previous day and change your pattern placements as needed. Then, go back to the current day and start with a new save file again to see if it worked.
It can be a tedious process but totally worth it in my opinion. I know it took me a long time to decide on where I wanted my villagers to go, but after that it took another hour or two to lay patterns all around my town. Good luck!