I was able to get serverless to generate my identity pool using the following:
IdentityPool:
Type: "AWS::Cognito::IdentityPool"
Properties:
IdentityPoolName: identitypoolname
AllowUnauthenticatedIdentities: true
CognitoIdentityProviders:
- ClientId:
Ref: UserPoolClient
ProviderName:
'Fn::GetAtt': [ MyUserPool, ProviderName ]
Hope this helps