After spending 20 mins faffing about trying to tie mine before my first dressage test I've gone and bought a ready tied one in readyness for my next test - can do without that kind of stress
They're brill. Slap the velcro together and put a nice pin in, sort of bunching the fabric up as you go. Job done. Equineck do some fabulous colours and designs.
They look awful, absolutely pointless. I have a shaped to tie one and I only compete in our unaffiliated riding club.
If you can't tie one wear a tie instead - much neater. Though to be honest tying a stock is not that difficult, you can get instructions on the internet and it is just two normal single knots. I can't tie a tie but I can tie a stock so I wear mine for everything!
If you are show jumping then a continental collar would do instead.