That would work, assuming you have updated the Pi4 for USB boot . You can follow this guide to do that. Any reference to SD card you can use your SSD. I have this method on a Pi3 and a Pi4 4gb, both work running off an SSD. You will get the “unsupported” message, however.
Alternatively, you can use one of the official HA images to USB boot. the 5.x versions for the Pi4 I believe are still in the Beta stage, but are working reliably for many, so could try one of them.
Follow the instructions HERE, but use the correct image for your Pi from HERE, most likely the image named hassos_rpi4-5.5.img.gz.