The probate court upon the receipt of any such application for appeal, shall forthwith notify the county road commissioners or the state highway commissioner in writing of such an appeal. The probate court shall thereupon make an order appointing the day of hearing upon such application, and shall require notice of such hearing to be given the county at large, if subject to assessment hereunder, to the several township boards of the townships interested, and to any city liable to an assessment at large, and the county road commissioners, or the state highway commissioner, at least 3 days before such hearing. Such notice may be served on the clerk of the board of supervisors, on the city clerk and upon the township clerks of the respective townships. At such hearing, the probate court shall thereupon make an order, appointing 3 disinterested and competent freeholders of such county, not residents or freeholders of the township or townships affected or assessed for the proposed improvement, as members of a board of review. The persons so appointed shall constitute the board of review. The court shall thereupon immediately fix a time and place where the said board of review shall hold its first meeting to review such assessments, which time shall not be less than 5, nor more than 15 days from the date of such hearing. The county road commissioners, or the state highway commissioner, shall thereupon give notice to the persons so appointed of their appointment, and of the time and place of their first meeting, and shall give notice of such first meeting by posting notices in at least 5 public and conspicuous places in each township within the assessment district affected by such assessment, and by giving notice to the prosecuting attorney in the county, in all cases where the state is an interested party. Said notice shall be served and posted at least 10 days before the meeting: Provided, That if the road to be improved, or the assessment district, shall lie in 2 or more counties, the application referred to in the preceding section shall be presented simultaneously to the probate court in each of said counties. Thereupon each said court, proceeding as above set forth, shall appoint a disinterested and competent freeholder of such county as a member of the board of review. Upon certification to him of such appointment the state highway commissioner shall fix the time and place of the first meeting thereof and shall give notice as above provided, to the members so appointed, of the time and place of such meeting. If but 2 counties are concerned, and if the members appointed therefrom are unable to agree, such members shall select a third member of the board, who shall be a competent and disinterested freeholder from another county of the state. Notice of such appointment shall be given to the state highway commissioner who shall notify the member so appointed thereof and thereupon the members of the board shall proceed in the same manner as is herein provided in the case of a board appointed within 1 county by the probate court thereof. In case of the selection of a third member of the board as herein provided the state highway commissioner shall fix the time and place of meeting of the board to be held thereafter and shall notify all members accordingly.