Stuck without an OS

Hi there! I have a unlocked Nexus 7 that used to be rooted. I did a wipe on it while it was rooted using TWRP and accidentally deleted the OS. Now when I turn my N7 on it just stays on the Google screen with the unlocked logo. I have tried using the Unroot + Flash Stock on Nexus Root Toolkit but I can't find the right driver as it can't connect to fastboot (And i am using the softbricked option). When I try to normally flash something it just goes to the google screen again and stays stuck. I need help with this!