Idaho Code § 22-301
Two (2) or more counties within the state may group themselves together and form a fair district. Petitions fully setting out their purpose, the number of counties to be included within the proposed district, and praying for the formation of such a district, bearing the signatures of not less than fifty-one per cent (51%) of the voters of each county, as based upon the total vote cast for governor at the last state election, shall be presented to the respective boards of county commissioners.
Upon receipt of such petition the clerk of each board shall give notice by publication for not less than two (2) weeks that petition has been filed and will be heard by the board at a day named, not less than three (3) nor more than six (6) weeks thereafter.
Idaho Code § 22-301