I was in this same boat earlier this year. The 2.5 SSD mount you're looking for is directly under wire shroud. It says Lian Li on the side. It you look on the underside of it, there are four slots to mount a SSD drive :-)
It's actually showing in the photo you posted above. I own the same exact model so, I'm speaking from personal experience. Just to be clear- In the opening message you say you salvaged a hard drive (HDD) but, then you say SSD. This location will allow for a 2.5 SSD but, not a HDD. Hope this helps.
Since this thread was posted last year, we have created a guide for this model. https://community.microcenter.com/kb/articles/373-how-to-add-a-2-5-hard-drive-to-the-lian-li-micro-atx-170-case
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