How to craft walls together at a corner when snap-in-place keeps attaching the new wall at the end?

I'm simply trying to attach two walls together to form a corner around a floor board. Instead of snapping in place at 90 degrees around the floor board, the new wall keeps attaching long-wise to the end of the existing wall. No matter how I rotate the new wall while placing it, the snap-in-place feature will not attach it to the floor board. What can I do to place the new wall to form the corner?

Instead of trying to attach to another wall at 90 degrees, try attach to another side of the flooring. If you are building without flooring you have to estimate and place it somewhere in position by your own judgement, or if you do not mind your walls slightly off ground you can place the flooring, build the walls in place then remove the flooring.

Some walls are not designed to form neat corners which is why you can find some corner pieces for structures. For walls that can connect to corner pieces you can actually use the corner piece to build the corner without flooring, but that will limit the types of wall you can use.