Howdy Johary, welcome to permies!
One of the things that I like to do is to go to the county assessor's web page of the county you are looking in.
If you are looking around Boise that would be ADA county. Which is
HERE
You will be looking at the County GIS map so look for GIS or interactive map.
This should take you to a map where you can zoom in and see property boundaries. If you play around with all of the "app" buttons on the page you can find out who owns the parcel, how big it is, taxes etc.
Might I suggest that you look for properties owned by the union pacific railroad. If you can find a contact person you can ask if they have any land for sale.
And yes it will take some time to walk around a larger parcel. I own 35 acres in Wyoming and we walked the whole thing in about 3 hrs. So if the property owner would allow you to drive around that might be quicker, but be sure that you have permission.
To find larger parcels that may not have addresses you will have to get yourself some good maps. Topographic maps are my favorite. Some states also have maps for sportsman that show land ownership. In the west the land was all surveyed into 1 square mile sections. At the corners of these squares there will be markers. many are cement posts with brass plaques mounted on the tops. These will have the township and range and section numbers engraved on them. So if you have a good topo map and you can locate one corner post you will know that there will be another post 1 mile in each direction, North, south, east and west from there.
I also like to look at the Landwatch website.
Any way I hope that helps some?