yes, exactly this.
You can also make an out of enclosure jungle gym for your boa to climb around on if you really want to ensure you are providing something (heck, even some chairs/stools and such work!) for when you have the boa out.
Will boas make use of shelves/perches? sure! How often they utilize is pretty dependant on the individual snake. I have found the smaller insular species will climb more, I've found younger snakes tend to climb more. Some love it, some really don't care and just want to sit in a warm spot on the floor. In general, I find common boas mostly hanging out on the floor of their caging, so with what I keep, I just provide some out of cage climbing options.