You didn't specify which Wooper, so I'm answering for both.
The real best method is to run an Encounter Power Water/Ground/Poison sandwich and use the date and time method to quickly reset for outbreaks (to clarify, when you have an Encounter Power sandwich active while your outbreaks reset, more outbreaks tend to share a type with whatever type Encounter Power was active). Getting the desired outbreak may take a while, especially if you're only using encounter power 1 or 2, and once you get the outbreak you will have to deal with a swarm of messages, but getting an outbreak of whatever you're hunting for is an efficient way to guarantee you get what you're looking for. Combining that with Sparking Power 3 gets you the best odds, although with Outbreak odds, you usually don't need Sparkling Power.
However, I have included some other methods if you are allergic to outbreaks for some reason. Note: you are responsible for getting your own Herba Mystica for Sparkling Power sandwiches.
Paldean Wooper
Your best bet is to run an Encounter/Sparking Power 3 Poison/Ground sandwich in South Province Area 1 where the lakes are at. Wooper spawns in the lakes and lacks the competition from Pokemon like Barboach you see in other areas. Another decent spot is the lakes in South Province Area 4 where Wooper spawns in and directly around the lakes, and aside from the occasional Toxel off to the side, you won't be seeing anything else.
You can also run a Poison sandwich in some of the lakes around Paldea, such as the one near Medali or on Glaseado Mountain, where a groups of Wooper spawn with a Clodsire. The swamp area in South Province Area 5 is also decent if you want to run a Ground/Poison sandwich there, where you get the group with Clodsire and regular Wooper spawns, as well as the occasional Mudbray and Toedscool/Croagunk, but the other options I mentioned are better for just Wooper.
Johtonian Wooper
Running an Encounter Power 3 Water/Ground sandwich in the Kitakami Road area (literally the starting area of the DLC) gets you just Wooper in the grassy areas. I personally recommend you use Ground, as in the little mud areas leading up to the town, you start to see Pokemon like Corphish with a water sandwich, but either way, a Ground/Water sandwich is the best way to hunt Wooper. With a Ground sandwich specifically, the rocky area in the river near the Mossfell Confluence fly point gets you just Wooper as well.
If you don't have the DLC (to anyone reading this that isn't the OP), there is an NPC offering a Johtonian Wooper for a Paldean one in Cascarrafa, and aside from trading for one online or transferring, this in-game trade is the only way to obtain a Johtonian Wooper in SV outside of the DLC, making the masuda method the only way to hunt this. Just make sure you attach an Everstone to the Wooper to get Johtonian Wooper offspring.
I hope this helped and you find your Wooper!
