This trading post is very easy to use but was mostly designed just for fun because it’s only one wide. It works as follows:
1) Go to the front of the trading post and put a diamond in the chest under the sign
2) receive your two gold ingots.

If you want to change the items just watch the last part of the video.

!!! This design has an item sorter so you can’t cheat and if you have a wall on both sides people won’t be able to take anything out of the trading post because it gives an item to the dispenser and dispenses it at the same time!!!