How to de-seed a watermelon? It’s summer and watermelon time. I know how to pick a good one (pro tip: a good greengrocer who has preselected the best batch on wholesale market). Then I cut myself a nice fat slice - and the problem starts. I am not a fan of watermelon seeds.
I grew up with watermelon served in wedges and then eaten by slicing off bite-sized chunks with a paring knife, removing the seeds as they appeared. But I would prefer to pre-cut the whole fruit in chunks, ready for portioning and then eating with just a fork or spoon.
No matter how I cut, there will always be seeds in the chunks and by the time I am done poking around with a paring knife, the pieces look like a crater landscape and there will still be some seeds left. Or I get small pieces floating in a lot of juice. Now, at home I can spit out the remaining seeds, but in the office, I’d rather spare my desk neighbor.
So how can watermelon be cut and deseeded cleanly and efficiently?

“Buy a seedless watermelon.” is explicitly excluded as an answer. Let’s focus on handling watermelons with seeds.
There are several hits on google, and many videos illustrating how to de-seed a watermelon.  Most have you cut the watermelon length-wise to expose the rows of seeds, which are generally in a circle down the center of the melon (imagining the pattern if you were to look through the end).  When you cut lengthwise, you expose the rows of seeds.  I prefer to remove both ends, and the rind first.  Then, slice in length-wise wedges.  You can often hold a wedge in both hands and gently break it along the line of seeds.  You can also cut the seeds out fairly easily this way, and create seed free pieces closer to the peel.  However, there is quite a bit of melon surrounding the seeds.  That, you just have to work at.