Set this page to have only the left side bar by adding the page name to the theme option left_sidebar_only.
import os
import themata
project = 'Milkish Doc'
copyright = '2020, Adewale Azeez'
author = 'Adewale Azeez'
html_favicon = 'favicon.png'
html_theme = 'milkish'
html_theme_options = {
'left_sidebar_only': [
'otherpages/leftpage'
]
}