You need to get rid of ALL the crystals.
Mine has been getting 44C for a couple of days, stirred at least 3x per 24 hours. (Hint: have a spare bucket ready for your stirrer!)
Then I strain it while warm through a 250 micron filter, and leave it to sit quietly for a couple of hours at room temperature, while the jars of seed go into the warming cabinet, set at 30C.
/// Even after this heating and stirring, the strainer does remove some crystals ... which is why I think warm fine straining is useful.
After the runny honey is definitely below 30C, the seed can be added and the batch mixed to uniformity.
Then its a matter of keeping it cool and frequently stirred until you think its setting (depends on your honey), when you need to get it into jars before it goes too solid! (Warming again to 30C - if needs be - should make it fluid enough to jar, if it is SOFT set ...)
/// Should have said that my "warming cabinet" (spare polyhive) has a fan to circulate and even out the warmth, but even so, to measure a typical average temperature within the cabinet, I arrange the temperature sensor to be about an inch away from the side of the bucket and about half way up the bucket (by simply looping the wire around the bucket handle!)
All this means that the temperature the STC1000 sees is as close as possible to reality.
Warming times in a waterbath (tea urn) can be much quicker than using warm air.