Crown Sliding is a technique that was found by ChaosBlasta and popularized by Phantom Phoenix. If the player does an initial dash (including foxtrot or dash dance) into the crown while the move is active, King K. Rool will "slide" while picking it up.
This is usually used for enabling combos from Crownerang, such as Crown Slide into down smash at 0% or an early up tilt at low to mid percentages. This can also go into Up Smash at Mid%s, potentially killing on stages with low ceilings. If a reverse input (usually done with the c-stick for ease of access) is used, it will reverse the slide, allowing for a sweetspotted forward smash during the combo. It can be charged for a period of time as well, greatly increasing its power. This can also be used for a down tilt aerial hitbox, forward tilt and up tilt on all variants of the slide.
It is possible to reverse a Crown Slide through inputting the opposite direction right after doing the normal input. This is known as a Reverse Crown Slide. This is made far easier with the C-Stick, although it is not required. If inputted correctly, King K. Rool will slide back roughly the length of his character backwards. This is a very important mixup option in tandem with forward smash, as it not only brings back K. Rool at a perfect distance, but also helps abuse the disjoint the move has harder than usual. Reverse Crown Slide also enables his neutral attack as a true combo at 0% for 33.6% in 1v1, while also generating a tech situation. As a result it is very possible to deal an upwards of 50% out of the gate abusing this tech and the situations Jab provides. Forward tilt and forward smash are also possible out of this, but they are generally considered to be suboptimal due to inconsistencies.
Up smash is true out of a Reverse Crown Slide on most characters from 20% all the way to around 85%, even regardless of DI with the correct spacing. It also works on lightweight characters from 0%, also hitting with the plank hitbox due to the low knockback in this scenario. It is also a kill confirm on said lightweight characters due to how long it lasts. The combo's consistency and power has lead to the playerbase calling this "Gang-Planking".
Crown Sliding is also a somewhat useful movement option in niche scenarios, being able to be used as a mixup option for getting around the stage or catching opponents off-guard. The short lag period leaves K. Rool a bit vulnerable however, making its usage debatable when approaching outside of chasing off-stage without a plan in mind. However, Reverse Crown Slide is a great tool in neutral and advantage, as the spacing it provides is perfect for mindgames and reads. As a combo enabler, Crown Sliding is a mainstay in King K. Rool's game plan and should be kept in mind by those looking to get into his technical side.