Along all four edges mark off inches: 0, 1, 2, ..., 7. This is a horizontal and vertical guide scale.
Now mark the horizontal measures 1 to 6. Also mark 1.5, 2.5, 3.5, 4.5, 5.5. 1 to 6 represent the centres of the stars in the 6-star rows, while the others represent the centres of start in the 5-star rows. By joining the top and bottom marks you will have 11 vertical lines.
Similarly mark horizontal lines at 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5. You now have a grid. The intersections of horizontal and vertical lines are the centres of the 50 stars. To mark them use crosses as follows:
The 6 columns are labelled 1, 1.5, 2, 2.5, ... to 6. The 9 rows are labelled 1.5 to 5.5. Call these letters A to I. The first row of 6 stars are at grid positions (coordinates) A1, A2, A3, A4, A 5, A6; the second row is: B1.5, B2.5, B3.5, B4.5, B5.5; and so on up to 9th row: I1, I2, I3, I4, I5, I6.
The grid lines will help to keep each star level. Assuming 5-point stars, two points will lie with these points aligned to, say, a horizontal grid line. The centre of the star will be slightly below the intersection so the left point will lie at 3/8" to the left of the intersection, and, of course, the right point will be 3/8" to the right of the intersection.
The stars will be separated along the rows by 0.25" measured from the rightmost point of one star to the leftmost point of the next along the row. The stars on the next row fit symmetrically in between the stars on the row above and there is room to fit without touching. The upmost point of the star on the lower row will be approximately 1/4" below the gap between the stars on the row above. The whole array is enclosed in the 7" by 7" with top and bottom margins of about 1.1-1.2" and left and right of about 0.6". Although the array is symmetrical, the centre of each star will be slightly displaced vertically downwards in relation to the grid marks, because the grid marks will be aligned to the centre of the horizontal line joining the upper left and right points of each star, rather than to the centres of the stars themselves.