Steps to make exactly the same rewrite rule without needing THE_REQUEST?

RewriteEngine On
# Rewrite multiple slashes with single slash after domain
RewriteCond %{THE_REQUEST} ^[A-Z]+\s//+(.*)\sHTTP/[0-9.]+$ [OR]
RewriteCond %{THE_REQUEST} ^[A-Z]+\s(.*/)/+\sHTTP/[0-9.]+$
RewriteRule .* http://%{HTTP_HOST}/%1 [R=301,L,NE]

Update: .htaccess location -
Rewrite action - rewrited to

What about this?

RewriteCond % ^(.)//(.)$ RewriteRule . %1/%2 [R=301,L]

Taken from here. (Regrettably I am not able to check it here).

Appears you will find no solution without Apache %{THE_REQUEST}.