Best Ways to Dodge

[Setharious]

I want to combine ancestral guardian barbarian with dwarven fortitude to really soak up some damage, so how best would I dodge them attack as a bonus action, or vice versa?

[PhantomSoul]

For 1 Ki a Monk (L2+) can Dodge as a Bonus Action, so that might be the easiest. Alternatively, with Haste, you could use your regular Action to Dodge, then you have your Hasted Action to make one attack (and a Bonus Action, e.g. if dual-wielding).

[JackPhoenix]

Scimitar of Speed allows you to attack with bonus action without using your regular action for attack. It's a very rare item, though.

[Man_Over_Game]

Adding on to PhandomSoul's answer, my recommendation is an Ancestral Guardian + Drunken Master build.

Drunken Master lets you run away after Flurry of Blows, is strictly focused on melee, and doesn't use much Wisdom.
Ancestral Guardian doesn't require you to stay near your enemy in order to maintain the taunt.

Combined, you can use Reckless Attack + Flurry of BLows to hit an enemy with Advantage on all of your attacks then running behind your team so the taunted enemy has no good options,
OR
You can hit the enemy with your standard attacks then use the Bonus Action Dodge to heal and stand your ground against the enemy.

As to why you'd use one over the other mostly depends on how many enemies you're dealing with and how many allies you can hide behind. If you're taunting the sole boss and your team can protect you, running is the better choice (as you severely cripple the primary target). If your team is scattered and frail and surrounded by multiple targets, it's best to stand your ground (so that you can guard with Opportunity Attacks and don't add Advantage to multiple attacks against you).