This is about using fondant texture mat to make soap. There are 2 kinds on the market, plastic sheets which are much cheaper, and the more durable silicone mats but cost far more. Plastic sheets tend to have simpler patterns while silicone mats can be as intricate as you can ever imagine. However, the common problem we run into is that it's hard to find fondant sheet big enough for our molds, they are not designed for soap makers for sure!
About 2 years ago I was lucky to saw this listing of a clear plastic texture sheet that has very nice wood grain pattern and the size is bigger than any I've seen out there. I bought one to try, but that batch of soap failed. I learned a lot from that experiment. These grooves are shallow, only about 1/16" deep at most. To cast a great impression the soap batter needs to be very fluid at pour but harden fast to get a perfect release. I admit I didn't have the patience to think about all these little details 2 years ago so I simply gave up after one failed try.
Making texture mat soap is somewhat different. It requires forehand preparation. Measure twice (sometimes 3 times) and cut once to fit the interior of the mold. In my case I used a silicone log (loaf) type mold and lined the mold with this plastic texture sheet on 3 sides to form an "U" shape. Simple clear tape was used to secure the sheets temporary to the mold. Then all I need is some simple 2 color ITP (in the pot) swirl and pour into the mold.