So, lets start with the basics:
First, ask your DM if you can take all the tasha's cauldron's optional abilities.
Foes slayer works well with your level 3 slayer's prey.
Then you should ask yourself if you want to be rather tanky or very offensive.
Since both abilities are once per turn, the question is, if you want dual wielding or twf. I'd probably go with two weapon fighting.
Then, I'd probably be variant human with two weapon fighting feat using two longswords.
My stat array would be:
STR 15 + 1
DEX 13 + 1
CON 14
INT 10
WIS 12
CHA 8
Using scale mail will give you a good AC of 17, +5 to hit, 2d8 +6 +1d4 + 1d6 damage if every attack hit at level 3.
I would probably not cast hunter's mark, as you need 2 bonus actions to get your abilities going. By then the combat might be over.
I'd also have a javelin ready to throw in the first round of combat.
One spell I like is longstrider, as it will help with positioning and speed for one hour and without concentration.
Absorb elements is never to underestimate.
Snare or alarm for the night.
So that is my recommendation. Have fun!