Where is the micro SD slot in my 2022 Prius prime LE (base model)

It should be shown in the Navigation Systems Manual. The nav system has it's own manual.
It looks like this on my 17 Prime Plus (base).
warnin bright mornin sun showin every dust particle on the dash -4 ^ C

 

This is NOT just another smart assed answer.............
You need to find that information in your users manual so that it will, hopefully, be correct for YOUR specific model.
Or ask your dealer with the car present.

Well meaning owners with all kinds of different models will likely give you answers that are WRONG for your specific car.

If it actually has the NAV feature, I would certainly think it would come with the chip installed.

 

If your car is a 2022 Prius Prime LE as stated, then you DO NOT have an in-car nav system, thus there is no map data in the head unit. Your car is equipped with Apple Car Play and Android Auto. Use your phone connected to the head unit via USB wire to use the phone's nav system. On the 2020 LE mode, the car came with the Scout GPS app that also required a phone app and wire connection, but IIRC, that app is no longer on the newer LE models.

EDIT: Oh, I just realized you are in Canada. I am not sure if the base model of Canadian PP is the same as the US version of PP LE. My info above is for the US version PP LE.

OP's car is a 2022 model. Toyota stopped in-car nav on the base (LE) model starting 2020, IIRC. My 2020 LE came with Scout GPS phone-based nav, but no in-car nav system.

 

I found the manual hard to follow in the beginning too, until I learned more about what the 2017 Prime Plus actually had for options and what it didn't have. The manual I have includes all the options available for all 3 2017 trims, Plus, Premium and Advanced. It was confusing at best.