diff --git a/slides/containers/Publishing_To_Docker_Hub.md b/slides/containers/Publishing_To_Docker_Hub.md
index 2e296fc7..c0d2ee5d 100644
--- a/slides/containers/Publishing_To_Docker_Hub.md
+++ b/slides/containers/Publishing_To_Docker_Hub.md
@@ -100,3 +100,25 @@ class: extra-details
 * In "Build rules" block near page bottom, put `/www` in "Build Context" column (or whichever directory the Dockerfile is in).
 * Click "Save and Build" to build the repository immediately (without waiting for a git push).
 * Subsequent builds will happen automatically, thanks to GitHub hooks.
+
+---
+
+## Building on the fly
+
+- Some services can build images on the fly from a repository
+
+- Example: [ctr.run](https://ctr.run/)
+
+.exercise[
+
+- Use ctr.run to automatically build a container image and run it:
+  ```bash
+  docker run ctr.run/github.com/undefinedlabs/hello-world
+  ```
+
+]
+
+There might be a long pause before the first layer is pulled,
+because the API behind `docker pull` doesn't allow to stream build logs, and there is no feedback during the build.
+
+It is possible to view the build logs by setting up an account on [ctr.run](https://ctr.run/).
diff --git a/slides/k8s/shippingimages.md b/slides/k8s/shippingimages.md
index 7e7245eb..2529a303 100644
--- a/slides/k8s/shippingimages.md
+++ b/slides/k8s/shippingimages.md
@@ -89,3 +89,25 @@
 - When picking a registry, pay attention to its build system
 
   (when it has one)
+
+---
+
+## Building on the fly
+
+- Some services can build images on the fly from a repository
+
+- Example: [ctr.run](https://ctr.run/)
+
+.exercise[
+
+- Use ctr.run to automatically build a container image and run it:
+  ```bash
+  docker run ctr.run/github.com/jpetazzo/container.training/dockercoins/hasher
+  ```
+
+]
+
+There might be a long pause before the first layer is pulled,
+because the API behind `docker pull` doesn't allow to stream build logs, and there is no feedback during the build.
+
+It is possible to view the build logs by setting up an account on [ctr.run](https://ctr.run/).
\ No newline at end of file