The way to do it is to add a device to the LXC container of the form

devices:

    <localhsarename>:

          path: <hosting_server_path>

          type: disk

There are two ways to do it. 

1) From the command line. The manual states

$ lxc profile device add --help 
Description: 
 Add instance devices 

Usage: 
 lxc profile device add [<remote>:]<profile> <device> <type> [key=value...] [flags] 

Examples: 
 lxc profile device add [<remote>:]profile1 <device-name> disk source=/share/c1 path=/opt 
     Will mount the host's /share/c1 onto /opt in the instance.
 

So, to mount the host’s /wwwdata/ directory onto /var/www/html/ in the LXD container named c1, run:

lxc config device add c1 sharedwww disk source=/wwwdata/ path=/var/www/html/

2) A second way to do it is to create a profile with that in it as (with the same data)

 

devices:

  lxcshare: 
     path: /var/www/html 
     source: /wwwdata
     type: disk

 

You can create the profile with 

lxc profile edit sharedir

then when creating the container use that profile e.g. 

lxc launch ubuntu:22.04/amd64 <containername> -p sharedir -p default