Slicing and seeding a capsicum the traditional way can take a while. If all you need is a few spears of capsicum, cut it like a chef: with a single slice around the edges.
Check out the video below to see the method in action: essentially, you just cut a single slice that continues around the capscium until you have separated the flesh from the core and seeds. This method leaves behind a fair amount of flesh on the top and bottom of the capscium, but you won't have to deal with deseeding the capsicum (or bell pepper, as our American cousins have it) and you'll end up with the main part of the flesh to use for spears.
How to Cut a Bell Pepper [Hatchery Co.]