Not Updated For Current Season
I get Ignite and exhaust as my summoner spells i know that undertow slows but the extra cc is nice since its the last thing i level up.
Start the game off with a ruby crystal, then giants belt, and eventually into the whole warmogs armor, i do this before i build anything including my boots, to gain an advantage of health right off the bat, then onto boots, boots of swiftness might also work well but i havent used them since you wont be doing much running away. Another Warmogs to get your health up to the near 5k your aiming for, An atma's because of the obvious, i got black cleaver next because honestly i had no idea what to get and it seemed to work, youd be hard pressed to get this far into a game but if you do i get frozen mallet the extra health helps with your W move and the fact that you should be unkillable
Undertow first for the cc and range, then VS and RS level up W as fast as possible keeping this order R>W>E>Q use w as much as possible, this build has no lifesteal and therefore it will be your only hope for health back, along with the bonus damage from your hp killing enemies shouldnt be a problem. I highly suggest a teammate be Blitzcrank idk why but they just seem to work well together
This is my personal Olaf build, its extremely expensive but once you get there your unstoppable, i would also note i only play 3v3's i have no idea how it fairs in 5v5's so feel free to let me know