The instructions below will work with the regular Git command-line tool or the hub CLI tool (makes things a bit faster).
# Make a new Sails app with a descriptive title
sails new sails-issue-cant-use-handlebars-layout
cd sails-issue-cant-use-handlebars-layout
# Install the minimum node modules needed to reproduce the issue, making careful note of versions
# and remembering to use --save and --save-exact
npm install handlebars@4.0.5 --save --save-exact
# Now make whichever are the simplest/quickest changes in your app which reproduce the issue,
# and when you for sure have the issue isolated, run:
git init
hub create # or use the GitHub UI to create the repo and `git remote add` it manually
git add .
git commit -am 'Reproduces issue with Handlebars layouts'
git push -u origin master
hub browse # or open the repo in your browser manually
# Then copy the URL of the new repo and paste it into your issue post.
# We'll check it out, and since this way we'll be able to experience the problem
# ourselves, we should have no problem getting to the bottom of it.