My front yard has a large patch of bare ground that seems to be incapable of supporting plants. The area has flooded in the past, though no longer does with improvements the city has made to the drainage in the neighborhood. I’m not sure if the soil is waterlogged or if some kind of chemical ended up in the dirt during previous floods. Either way, the area won’t grow anything, not even weeds. This is an L shaped area, about 50 square feet. My idea is to make a border with bricks, fill the area with several inches of topsoil, and then plant some plants. Given that the area has been a patch of dirt / mud for a year or so now, would this idea likely work? Would I be better off filling the whole area with something like lava rock? I’d appreciate any advice any of you all can give. Thank you 
Using just topsoil would be a mistake: too heavy; reduced drainage; air wouldn’t circulate as well. All leading to rot and you losing much of what you plant, to be replaced by moss and weeds and other less-desirable plants. Do yourself a favor and get some actual planting mix(soil with organic matter added, and some sand, or other inorganic materials for drainage, every company does it differently), whether a few bags if the site is small or arrange for a truck to deliver some if you’re planting the front 40. You’ll have to work in some organic matter occasionally as it disintegrates. Just like Mother Nature does.
It’d be worthwhile to turn over or rototill the soil on the raised bed site at least a few inches deep (if it’s compacted, roots reaching it from the raised bed plants will remain shallow and susceptible to drought).
I second the idea of not using plain topsoil, but instead a planting mix with organic amendments from time to time. I periodically composted manure, shredded leaves and lightweight soil mix from discarded houseplants to my beds (there are two, about a foot deep).
If there’s any serious concern about metals/contaminants in the soil underlying the proposed raised bed (i.e. if you live next door to a Superfund site :eek:), you can get a soil test done (state agriculture/university horticulture depts. can probably do them or tell you where to go).
Oh, and using lava rock to cover an area as mulch or for decoration is a colossally bad idea in my experience. I once rented a house that had lava rock in the front beds, and lots of weeds germinated in it, plus the rock tends to scrape your hands when you pull out the weeds.