SlackBuildsOrg/graphics/pencil3

Pencil is built for the purpose of providing a free and open-source
GUI prototyping tool that people can easily install and use to create
mockups in popular desktop platforms.

Warning: This SlackBuild requires network access when it runs, meaning
it downloads files from the Internet with root access. You should
decide for yourself whether or not you think this is a good idea.

Optional features:

ELECTRON (default=no): This requires electron, available in SBo. Use
pencil3 with some version of electron previously installed in the
system.  Otherwise the SlackBuild uses and downloads electron required
for pencil3.

BINARY (default=no): Use it to create a binary package. This option
requires downloading electron for the architecture of your system,
close to 40MiB.  You can install the electron package from SBo with
the INSTALL_ZIP=yes option, to avoid the download.

If you need to use any option do something like:

  ELECTRON=yes ./pencil3.SlackBuild