That's a fine way to go but it will make things more difficult for you too. I use standoffs for remounting circuit boards and other stuff. Your toolkit should a drill, Dremel, and craft knife. Those will help with cutting slots and squares, etc.

Those missing hex nuts will be a problem. There's really no way around it. Maybe you can find replacements at the hardware store?

https://www.amazon.com/iUniker-Raspberry-Installation-Standoff-Accessories/dp/B09PD2D5XB/ref=mp_s_a_1_1_sspa?crid=HJYJRZ3CF8LQ&keywords=Standoffs&pd_rd_r=48482f2d-2c2a-42c9-9e25-38c2b18ad6d6&pd_rd_w=CUw3k&pd_rd_wg=YsLUl&pf_rd_p=1d685bfc-540c-4c38-945c-0ff8e8788608&pf_rd_r=NST0P8ZC5CZSKZW8ARG5&pid=BMxx27M&qid=1647560335&refinements=p_n_feature_twenty-three_browse-bin%3A19047482011&s=industrial&sprefix=stand+offs%2Caps%2C311&sr=1-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzODJRUUlTVEM2QUk5JmVuY3J5cHRlZElkPUEwNTQyNzAwM0g0NlU1TVJLSEhTMSZlbmNyeXB0ZWRBZElkPUEwMDk1NTM3MzRTSTNLRk9CWTRCNSZ3aWRnZXROYW1lPXNwX3Bob25lX3NlYXJjaF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl