This is how I made mine. I created a cluster named 'free-cluster' which runs 2 nodes. These nodes are in 'us-west1-a' as the 'free' tier only allows for the us-east, us-west and us-central zones only. also the VM instance-type should only use 'f1-micro' as that is the freebie they give. the rest are paid.

As is pointed out, GCP does force us to create 3 nodes and no option to state this in the dashboard. But after that you can just go to the nodes and "cordon" and "drain" them so they will not consume the free compute fast. You can leave just one node for the free-tier... this however makes less sense as you will not take advantage of load balancing, self-healing and other features as to why we use kubernetes clusters to begin with. for me I am good testing on 2 nodes as I only need to pay for that 1 cheap monthly f1-micro for my hobby and learning. make sure to go to Google Compute Engine in the dashboard and open the 'Instance groups' in the sidebar, you will find the VM instances in that cluster which you can just delete by selecting and clicking the "Delete Instance" button.

As I understand, Google allows 1 f1-micro instance to be used for free even after the 12 month free period.

Yes, you can use GKE with the free tier. GKE only charges for the underlying compute engine resources, which are directly billed by compute engine. (Note that after June 6, 2020, the free tier only includes one free GKE zonal cluster -- not an unlimited number of clusters).

GKE will likely require you to run 3 free f1-micro instances concurrently to get the cluster to a minimum size, but as long as the cluster is in one of the free regions and the total usage in a month is under the total number of hours per month it will still be free (that is, you can run 3 f1-micros for a bit under 250 hours and still be in the free tier). Make sure to shut off your instances when you are not using them. See more at https://cloud.google.com/free/docs/gcp-free-tier#always-free-usage-limits (especially the notes about the limit being time rather than instance count).

You may also want to ensure that the persistant disks are not kept around while the cluster isn't running, as the free tier only allows 3 10GB disks over the course of the month.

If you happen to run over the usage, you will only be charged for the usage beyond the free tier.

Of course, this all assumes that f1-micro instances are suitable to your use case. They are quite limited, and once GKE is on them, they have almost nothing remaining in terms of RAM: https://cloud.google.com/kubernetes-engine/docs/concepts/cluster-architecture#memory_cpu

Finally, it has been my experience that setting up the stackdriver support when you create the cluster if you only have micro instances can cause the cluster to struggle greatly -- the stackdriver monitoring alone (or with even minimal other applications) start to cause the nodes to be throttled and time out.

For now It's not possible to create kubernates cluster with one f1-micro. It requires minimum 3 f1-micro instances:

ERROR: (gcloud.container.clusters.create) ResponseError: code=400, message=Clusters of f1-micro instances must contain at least 3 nodes. Please make the cluster larger or use a different machine type