diff --git a/Dockerfile b/Dockerfile
index 790e671..4569f50 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,10 +4,12 @@
 # ===========================================================================
 #   Update the source image.
 # ===========================================================================
-FROM gentoo/stage3:amd64-nomultilib-systemd as bootstrap
-# Migrate to a merged-usr form.
-RUN emerge --quiet-build=y --oneshot merge-usr
-RUN merge-usr
+
+FROM scratch as bootstrap
+# Unpack the stage3 archive (which is downloaded and verifed externally).
+ARG ROOTFS_FILENAME=""
+ADD ${ROOTFS_FILENAME} /
+# Set the profile.
 RUN eselect profile set "default/linux/amd64/17.1/no-multilib/systemd/merged-usr"
 # Replace /etc/portage/make.conf.
 RUN rm --one-file-system /etc/portage/make.conf
diff --git a/build-image.sh b/build-image.sh
index 4f2e489..5524e4c 100755
--- a/build-image.sh
+++ b/build-image.sh
@@ -12,10 +12,15 @@ IMAGE_TAG="${REGISTRY}:${VERSION}"
 
 REPOS="${REPOS:-/var/db/repos}"
 DISTFILES="${DISTFILES:-/var/cache/distfiles-podman-1}"
+DISTFILES_STAGE3="${DISTFILES_STAGE3:-distfiles}"
 BINPKG="${BINPKG:-/var/cache/packages-podman-1}"
 LOGDIR="${LOGDIR:-$(pwd)/log}"
 DOCKER_FILE="${DOCKER_FILE:-$(pwd)/Dockerfile}"
 
+ARCH="${ARCH:-amd64}"
+MICROARCH="${MICROARCH:-amd64}"
+OCI_ARCH="${OCI_ARCH:-linux/amd64}"
+
 PODMAN_BUILD_ARGS=(
     # Do not leak the host's /etc/host into the container.
     --no-hosts
@@ -34,11 +39,16 @@ PODMAN_BUILD_ARGS=(
     -v "${LOGDIR}:/var/log:rw,U"
     # Use the given OCI file/Dockerfile.
     -f "${DOCKER_FILE}"
+    # Add details about the architecture.
+	--build-arg ARCH="${ARCH}"
+	--build-arg MICROARCH="${MICROARCH}"
+	--platform "${OCI_ARCH}"
     # Tag the generated image.
     -t "${IMAGE_TAG}"
+    -t "${REGISTRY}:latest"
     # Label the image.
     --label="gentoo-nfr-${IMAGE_TAG}"
-    # Sign the image.
+    # sign the image.
     #--sign-by="${GPG_SIGNING_KEY}"
     # Rebuild everything w/o cache.
     --no-cache
@@ -55,17 +65,43 @@ _mkdir()
   mkdir -p "${@}" || exit_err "Could not create dir ${@}."
 }
 
+# === Prepare all directories.
 _mkdir "${REPOS}"
 _mkdir "${DISTFILES}"
+_mkdir "${DISTFILES_STAGE3}"
 _mkdir "${BINPKG}"
 _mkdir "${LOGDIR}"
 
-podman pull gentoo/stage3:amd64-nomultilib-systemd || exit_err "Could not fetch the image."
-podman build "${PODMAN_BUILD_ARGS[@]}" || exit_err "Build failed."
+# === Fetch the stage3 file (and verify it).
+# Note: This uses some nasty string manipulation assuming a certain structure.
+#       If upstream changes the format, things will break here, again.
+SERVER="https://ftp-osl.osuosl.org/pub/gentoo/releases/${ARCH}/autobuilds"
+MY_STAGE3="latest-stage3-amd64-nomultilib-systemd-mergedusr.txt"
 
-# Update the tag 'latest'.
+# Fetch the stage3 archive and its signature.
+curl -sLC- -O --output-dir "${DISTFILES_STAGE3}" "${SERVER}/${MY_STAGE3}" \
+  || exit_err "Could not download the pointer file for the stage3 archive."
+gpg --verify "${DISTFILES_STAGE3}/${MY_STAGE3}" \
+  || exit_err "Could not verify the download pointer file."
+
+LATEST_ARCHIVE="$(grep $(echo ${MY_STAGE3} | sed 's/latest-//;s/.txt//') ${DISTFILES_STAGE3}/${MY_STAGE3} | cut -f1 -d' ')"
+ARCHIVE_FILE_NAME="$(echo ${LATEST_ARCHIVE} | cut -f2 -d'/')"
+
+curl -sLC- -O --output-dir "${DISTFILES_STAGE3}" "${SERVER}/${LATEST_ARCHIVE}" \
+  || exit_err "Could not download the stage3 archive."
+curl -sLC- -O --output-dir "${DISTFILES_STAGE3}" "${SERVER}/${LATEST_ARCHIVE}.asc" \
+  || exit_err "Could not download the stage3 archive signature."
+
+# Verify the signature.
+gpg --verify "${DISTFILES_STAGE3}/${ARCHIVE_FILE_NAME}"{.asc,} \
+  || exit_err "Could not verify the stage3 archive."
+
+# === Remove the old tag 'latest'.
 podman tag rm "${REGISTRY}:latest" # Do not exit_err here. At least on first run
                                    # there is no latest tag to delete.
-podman tag "${REGISTRY}:${VERSION}" "${REGISTRY}:latest" || exit_err "Could not tag new image as 'latest'."
+
+# === Build the new image.
+podman build --build-arg=ROOTFS_FILENAME="${DISTFILES_STAGE3}/${ARCHIVE_FILE_NAME}" \
+  "${PODMAN_BUILD_ARGS[@]}" || exit_err "Build failed."
 
 # vim:fileencoding=utf-8:ts=4:syntax=bash:expandtab