When using double sided tape underneath the interlocking floor tiles, where should the tape be positioned relative to the tiles? For example, should the tape be positioned under the edges of adjacent tiles to keep the seem together, or should the tape be placed so it goes through the center of the tiles?

If you are going to adhere the Tatami Tiles to the ground you would want to ensure that it gets the maximum grip possible. The best way to ensure that a large section of flooring will stay stable when used is to create a grid of double sided tape that runs at 45-degree angles that creates an "X" shape through the tile.