I was able to successfully build and modify the delay of the blink firmware! One trip up I had was that I can only

make flash

once per powerup. Further

make flash

attempts result in:

************************************
verifying...
************************************
status reg_1 = 0x0
status reg_2 = 0x2
setting address to 0x0
addr 0x0: *** read compare FAILED ***
b'6f00000b13000000130000001300000013000000130000001300000013000000232e11fe232c51fe232a61fe232871fe2326a1f
e2324b1fe2322c1fe2320d1fe232ee1fc232cf1fc232a01fd232811fd2326c1fd2324d1fd2322e1fd2320f1fd130101fcef000011
8320c1038322810303234103832301030325c1028325810203264102832601020327c101832781010328410183280101032ec1008
32e8100032f4100832f0100130101047300203013010040170500001305c5f6731055301305000093050000171600001306864363
0cb500832606002320d50013054500130646006ff0dffe13050000930580006308b50023200500130545006ff05fff'
<----->
b'0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000'
make: *** [../common/common_makefile.mk:38: flash] Error 1

After a power cycle I am again able to successfully run

make flash