Working backwards, delete all manually created resources.
aws autoscaling delete-auto-scaling-group --auto-scaling-group-name myEC2Workshop --force-delete
aws elbv2 delete-load-balancer --load-balancer-arn %loadBalancerArn%
aws elbv2 delete-target-group --target-group-arn %targetGroupArn%
aws ec2 delete-launch-template --launch-template-name myEC2Workshop
Finally, delete the CloudFormation stack itself.
aws cloudformation delete-stack --stack-name myEC2Workshop