Warning: do not use no english names in paths!

Local building for x86-64 (Host: Ubuntu 20.04 64 bit):

sudo snap install snapcraft --classic
snapcraft

Local building for arm64 (Host: Ubuntu 20.04 server 64 bit - https://ubuntu.com/download/raspberry-pi)

sudo snap install snapcraft
SNAPCRAFT_BUILD_ENVIRONMENT=host snapcraft

Install local build:

sudo snap install ponysay_3.0.3_amd64.snap --dangerous

Publishing:

snapcraft login
snapcraft push --release=stable ponysay_3.0.3_amd64.snap