This is the Biggest Risk
I've come across one or two cases where the opponent used his cue to leave a chalk mark on the cloth just behind the desired contact point, it's quite a subtle illegal trick one should be looking for, it's not obvious like leaving a cue on the table.
I have seen players lay their tip on the table along the contact point and extended line the object ball will travel then swing the back of the stick to the line the cue ball will take to get to the object ball. If you are a player that uses a lot of chalk and may chalk three or four times as you go through your preshot routine over and over on a tough shot it is easy to put a tiny mark on the table. Most don't use this mark but it is still illegal to make it. Some do use it too, I have had this crap pulled on me in tournaments.
If you are marking the table, even accidentally and incidentally, it is illegal. Nobody can prove if you are using the mark or not but a disturbance that takes one or both players out of their game is very possible.
If somebody moves their cue tip on the table after just chalking they are very likely to commit a foul even if totally unintentional. Some deliberately put a mark at the point the center line of the cue ball will be when it strikes the object ball. I see this on back cuts more than most shots. I would call this myself if someone did it repeatedly.
I watched a very ethical player trying the technique of building most tough shots with the tip of the cue on the table. He wasn't deliberately marking the table or using the mark but if someone called him on marking the table they would have likely been correct.
Foul, no foul, hard to say. Depends on the rest of your routine. I use my eyes in a very similar manner, not involving the stick. Doing it without the tip of the stick ever touching the table removes any question of unsportsmanlike behavior.
I learned to deal with slow players over the course of several months long ago. Cost me a few hundred dollars in small bets, paid me back literally thousands over the next eight years or so. Taking a long time on every shot may annoy some players but most don't care as long as you are doing something and not taking an eternity on even the simplest shots.
I would practice working with locking your eye on a particular spot on the cloth and not involving the stick on most shots. However, I know of no rules in any association that makes your technique illegal unless you are marking the table or the stick leaves your hand. As has already been mentioned, you may be called for slow play especially if you are known to cobble up the flow of a tournament by all of your matches running long.
Hu