Preheat oven to 350°F. Wrap the outside of each 4-inch springform pan thoroughly with 3 layers of heavy-duty aluminum foil, ensuring the foil comes up the sides of the pan. Spray the inside of the pan with nonstick cooking spray.
Combine graham cracker crumbs and sugar in a bowl, stirring to combine. Add the melted butter and mix with a fork until the texture resembles wet sand. Divide the mixture evenly between the pans and press it firmly into the bottom of each pan. Bake for 10 to 12 minutes, until the edges begin to lightly brown. Transfer to a wire rack and cool completely. Reduce oven temperature to 325°F.
Beat cream cheese, sugar, and flour on medium speed until smooth and combined, about 1 minute. Scrape down the sides and bottom of the bowl. Add sour cream, vanilla, and salt, and beat on low until just combined. Add eggs one at a time on low speed, mixing just until each is incorporated. Scrape the bowl between additions. Do not overmix.
Divide the batter evenly between the eight pans, filling each about ¾ full. This leaves enough room for the cheesecake to rise slightly without spilling over. Place the foil-wrapped pans into a large roasting pan, spacing them slightly apart so water can circulate around each one.
Place the roasting pan on the center oven rack. Carefully pour hot water into the roasting pan until it reaches about halfway up the sides of the springform pans.
Bake at 325°F for 25 to 30 minutes, until the outer 2 to 3 inches appear set and the center has a controlled wobble when the pan is gently shaken.
Turn off the oven and crack the door open about 1 inch. Leave the cheesecake in the water bath in the oven for 1 hour.
Remove the roasting pan from the oven. Carefully lift each cheesecake out of the water bath, remove the foil, and place it on a wire rack. Run a thin paring knife around the edge of each cheesecake to loosen it from the pan.
Cool at room temperature for 2 hours, then cover and refrigerate for at least 8 hours or overnight before serving.