Faith, Creationists have been trying to do this for the last 200 to 300 years. Scientists and naturalists, whose reality included the Biblical flood, had the scientific skills to look for it in the rock record. They could not find it then and the current ones have not been able to find it still.
You, an armchair geologist (no offense) with a naive understanding of geological processes, will certainly never find it on the computer or in your Creationist literature, or even arguing on EvC. Those of us who have studied the earth and walked the rocks, are not trying to deceive you and neither have we been deceived. No one has told us what we have to believe. It's just there, in front of our eyes, and we, as people/scientists with intellectual honesty and integrity, cannot deny what the earth is showing us.
And it's not like this person is basing that interpretation on something he's pulled out of his ass. He's basing it on previous research which suggests that deposition of the strata takes time, burial-compaction-lithification takes time, uplift takes time, and cutting it with a river takes time.
The weight of the stack, some two miles deep or so, put pressure on the lowest layers in conjunction with the volcanic magma and heat from below, to form the granite and schist.
So you're suggesting that schist and granite only occur at the bottom of the rock column? I suggest you do a little research on schist and granite and buried flood basalts, and consider retracting that silly argument.
I'm addressing your suggestion that schist and granite were formed following the great flood as a result of compression and heat due to the overlying sediments. In OE, that's certainly possible, though you'd have to add a whole lot more overlying sediment and tectonic stress. But large amounts of granite and schist are found exposed on the surface of the earth today, mostly in mountain ranges. Sometimes, very large mountain ranges.
How did these rocks form without the overlying sediments to bury, compress, and allow them to cook deep in the earth?
Granite is a plutonic rock which forms from the cooling and crystallization of magma in the subsurface, generally, several kilometers deep. Granite has a medium-grained texture, meaning you can see the individual minerals forming the rock.
Volcanic rocks cool and crystallize in the surface or near-surface environment, and tend to be finer-grained. Rhyolite is the surface/near-surface equivalent of granite.