I have a 220 outlet in my carport with a weatherproof cover and the BMW Turbocord charger. Instead of the 220v adapter, I bought a short extension cord with a NEMA 6-20 plug and a 5-15 receptacle. The charger hangs off the cord off the floor. It's under a carport with shelter from the rain.
I ran cabling to my carport a couple of years ago, alas, I only had 10 gauge cable pulled. As a result, the biggest circuit I could support was a 20 amp circuit. I miss out on charging at 32 amps, but 16 has been just fine so far. If I'm in a pinch, there's a DC charger a half-mile away.
I don't see a need for a wall box, although nowadays they're a good selling point for your house.
A wallbox is relatively theft-proof, which is nice. I used to leave my Prius charger coiled up in my carport and expected it to be gone one night. It never was. Regardless, I store the TurboCord in my trunk when I'm done.