Sorry for not checking this thread in a while. Real life, blah, blah, blah. Lol. But I am sorry there are questions out there about the technique and I have missed answering.
I went and double checked in my game and both of the techniques still work and I am patched all the way up to the current patch. I do have a couple ideas where there may be some difficulties and let's hope it sorts the problems out. I was testing on a lot where the active household of sims were living. I did not test on an unoccupied lot while in "edit town" mode.
AmalahRose: After you do the "ctrl" while drawing the pool to erase the walls of the basement, you have to go back and draw the pool in normally up to the edge of the basement. If you have done that step and the game isn't drawing them together, my best bet is that the ground where you are drawing the pool and the ground where you are drawing the basement are not exactly the same level. Try erasing both, then leveling the entire area where you are building both together, then try the techniques and see if that helps.
One thing I did notice too while testing and I don't know if this came with an update or not. When you hold down the "ctrl" key while drawing the pool to erase the walls of the basement, you have to hold down the "ctrl" key before you start drawing anything with the pool. So hold the "ctrl" key, then draw your pool up against the basement to erase the basement wall. The pool shouldn't actually draw when you release the mouse button from drawing the pool, but the basement wall where you drew pool against it should be removed. Then once the basement wall is removed, you can use the pool tool normally to place the pool against the basement.
I hope this helps.
