I'm not going to get all fancy with my build. I'm just going to explain what works for me.
Olaf is a freaking viking. From what I've understood while growing up is that vikings are similar to berserkers. They feel no pain and only live to fight. Then I wonder why Riot's recommended build for Olaf makes him squishy as hell..

So I devised my own build.

First off, you must be wondering why CD boots?
In case you didn't know, Olaf deal true damage. 340 every 2.4 seconds at 40% CD. Lets say an average team fight last around 30 seconds that gives Olaf the time frame to deal approx 5100 true damage. DAMAGE THAT IS GUARANTEED. Not even Rammus' Ball Curl nor Alistar's Unbreakable will stop this damage.

Now back to the actual guide. I start with Mana Gem and two health pots. This gives Olaf some decent lane time as at level 2 he may start last hitting and harassing well with his Undertow. FOCUS ON LAST HITS MOAR THO! x) . Once you have enough, b for a catalyst of the protector.

This should allow maximum lane/farm time, see Catalyst Passive.
Around Lvl 6 Olaf should be dealing around 280 Damage with reckless swing. Feel free to gank or jump someone in lane. Champs at this lvl should still have around 600 health, while Olaf should have about 1.1k

Play comfortably. Focus on last hits and gank an over confident mid whenever you can.

Next we make our glacial shroud, more CD! This should bring our Reckless swing to a less than 3 second cd while Pumping the 340 true damage.

This is just the jist of the build, I would like to go more in depth and hold your hand from 1-18 but I just don't see that as being wise.

Set priority for banshees or Frozen heart as you see fit, once completed with those go into Warmong for some delicious health. By this point you shouldn't be getting focused because of high resistances. Ult makes you "Immortal" so feel free to rush their carry and bash their face in.

The Trinity.
Super Important. With Olaf's Vicous strikes and Atma's proving health Olaf should have 300 AD up Constantly. Because his True Damage has near the exact same CD and the Internal CD for Trinity he should be able to create a substantial amount of damage even without many AD items.
His high survivability is also a huge boost to his sustainable non burst damage.

End Game. Grats, your q at melee range( Olaf's effective range) has a 0 second cd. Be amazed at how often you can spam it. Second I usually tend to drop my Veil and grab a Force of Nature. Extra movement speed and crit help keep damage on opposing carries.

I apologize for lack of glam in build, but I have whatever it is you want at the core. Before you mock this build, I highly suggest you try it.

PS. My team and I adopted the new Meta Game team. Trinity Tank/ Off Tank is very crucial in our team comp. Olaf is able to solo as well. Q is amazing farming tool/ Harass.

Cheers.