surface contact between two parts

hey guys! I am modeling Park bench and found this tutorial :

https://youtu.be/xhZQK_eknWU

I am not 100% sure that this is what I need so I am asking you for advice, step by step solution or some useful link on how to model this problem.

As you can see on pictures below force will be aplied on wooden board and then thru them on steel construction. How can I acuratly model this contact surface?

I found some contact tie tutorials which work but contact tie fuses those two surfaces and I am not sure if that is valid in this example.