Hi Mark yes you can use crushed corn instead of flaked corn but you will need to boil the crushed corn on the stove with double the volume of water to crushed corn till the starches are converted to sugars. Very much like making "grits" & any grits recipe would be a source of info.
Then incorporate the converted corn into the start of your mash & you should do fine.
Flaked Maize is pre-gelatinized and mash ready & crushed corn is not.
Any more questions please email me.
Happy brewing,
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The Czar