Multi-stage build for R application

I'm trying to create a multi-stage build for an R application based on rocker/r-ubuntu:20.04 image.

The reason that I'm based on that image is to install binary packages via apt-get as suggested in order to improve building time.

If I build the image without multi-stage build, the final image size is 2.32GB, so i need to decrease the final size with multi-stage build.

The approach that I follow is create an alpine:latest image and copy the app folder from builder, and the R libraries installed (/usr/local/lib/R/site-library/) and the binaries packages located in /usr/share/doc.

The final image doesn't work, because no commands to execute the app is installed.

The Dockerfile is the following:

FROM rocker/r-ubuntu:20.04 as builder


# # system libraries of general use
RUN apt-get update && apt-get install -y \
    pandoc \
    ...
    libxml2-dev 

RUN apt-get update && \
    apt-get install -y -qq \
    r-cran-config \
    ...
    r-cran-tidyverse 

RUN R -e "install.packages(c('other-packages'), dependencies=T)"    


# copy the app to the image
RUN mkdir -p /root/bloomapp/tmp
COPY . /root/bloomapp
COPY .Renviron Rprofile.site /usr/lib/R/etc/


FROM alpine:latest

#Copy app to alpine
COPY --from=builder /root/bloomapp /root/bloomapp
COPY --from=builder /usr/local/lib/R/site-library/ /usr/local/lib/R/site-library/
COPY --from=builder /usr/share/doc /usr/share/doc

WORKDIR /root/bloomapp/

EXPOSE 3838

Is reasonable this approach? or exist any other better way to do multi-stage build for a R app image?

Thanks.