I found myself having difficulty "discovering" the fields from my custom connector.
The api I am using does not appear to have their dictionary set up so that flow can get the field columns dynamically.
As a result I thought it was not possible, however I found that dynamically is not possible but with parse JSON it is.
I had tried parse JSON with no luck, except this time I tried something different I pressed the link "use sample payload to generate schema..." under the text box.
It is not clear on the interface that pasting into the box and pressing the link to generate the schema are two different methods.
I figured pasting the payload JSON would figure out the schema but it was not so, you have to click the link.
Anyhow I can get my fields now, makes it much easier for anyone else who also needed help with this: