Looking to add object mid Air without plane recognition using ARFoundation

Lately i've been looking on the features implemented by Unity on ARFoundation. I'm trying to instantiate coins in midAir according to the position i have based on the camera, adding each coin by a touch screen event. The problem i'm realising is i have to use Raycast and plane detection in order to be able to instantiate a prefab object. Has anyone managed to do anything similar? i can post the code i have so far if anyone can help me.

Thanks in advance.

 

I didn't try this but.

So I'd like to also know how will Foundation do it.

Using the Mira Prism SDK or the Holoboard SDK When placing a game object at (0,0,1) sets it hanging in midair. And that's just positional tracking (distance from headset).
Similarly, are you trying the hang the coins in the air per-distance from the back camera? Because obviously they anchor to nothing in the physical world.