Okta SAML2 Integration

Hi
I am trying to setup Okta integration with my front end app running in my localhost.
And using service provider as backend service to handle SAML responses.
I am stuck at setting up config at Okta side and have entered Single Sign on URL of localhost frontend app.

My frontend service is running on localhost:3000
Backend service ( masked real name)

On testing configuration it is failing at last step → saml redirection and trying to POST Saml assertion to http://localhost:3000/login/saml2/sso/okta
( It looks it is going via URI and hence the issue with payload sizing?)

Could you please help here.. It appears we would need to add service provider’s details on SAML2 setup
i.e. https://service1.abc.com /
?

Single sign-on URL : http://localhost:3000/login/saml2/sso/okta
Audience URI (SP Entity ID) : http://localhost:3000/saml2/service-provider-metadata/okta

These are the current settings in Okta SAML 2.0 setup

The Service Provider App ( Spring boot ) which I am currently using is old Spring Boot version 1.5.9.RELEASE