There are only three things which differ from my build that I have used successfully many times:
1. I use "full_flo-userdebug". Never tried the aosp flavor. Also, you transposed the underscore and the dash in "aosp-flo_userdebug". I assume that's not actualyl what you tried to build with. It should be "aosp_flo-userdebug".
2. You installed with "fastboot -w flashall". Since I like to use Teamwin recovery, and I don't want to overwrite it every time, I install the cache, userdata, boot, and system partitions individually, like "fastboot flash boot boot.img".
3. I use version 4.4.1_r2. I'm not sure how well 4.3 supports the Nexus 7 since I don't have any history with it. I've installed 4.4.1_r2 at least thirty times, and I've done months of extensive embedded testing with it in place,
Otherwise, your build should work. I've never had to build a kernel specifically.
NOTE: By the time the logo appears, ADB should be running, so you should be able to get a logcat from it. Perhaps you can find out what's going wrong.