Start with Death or Glory, it depletes your def but with 60 you are able to stand up first boars attack and build up ini to 5 before switching to Oak Stance. Meanwhile your first Dash cooldown finsihes and with next you have 6 which is enough for Flex.
Then use flex/OakStance to keep your defence up and when you attack is lower switch to Bloodlost (careful for incoming attacks though, switch to Oak when the boar has high attack bar). When your attack is full switch to dash/charge (dash is safer, charge is quicker) and build up your ini to 16. Boar will gain one or two advantages at that point, but you will get it back with Invocation of Skuld. threetimes, bringing you to INI7.
At this point the battle pace is at 10 which is good for fast flexing up attack and you can start punch/flexing him. Sometimes I build up another three inis to use one more invocation and to get more advantage. As soon as you get him to low defence, you gain adavntage by punching and it is two max three punches to make him run.
Stay near water, short lag you got hit and you run to water, big lag... well starting room with runestone

Boars are comfortable around UA 70-75