Thanks Jici, got it to work using Integromat.

I see why Slack has defined the endpoint the way they have.
Its cos, all interactions(click of button, submit of form etc.) hit the same endpoint with a payload.

Now my issue is that the since the same endpoint is hit on bubble and based on payload content(which is processed on Integromat) have to take different actions.
But Integromat needs json definition.
So its a chicken and egg problem now.
I am sure there is a hack to solve this, but it just feels like too many hacks.

So would evaluate other options.
Thanks for the help!