The next step could be as simple as:
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^/]+)/([^/]+)$ page.php?categ_slug=$1&slug=$2 [QSA]
The next step could be as simple as:
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^/]+)/([^/]+)$ page.php?categ_slug=$1&slug=$2 [QSA]