Now it got confused..
I think Larsas' solution is perfectly fine when it's laminate or stone slabs.
When joining wood strip boards or lengthwise patterns, it's more aesthetically pleasing if the joint is made at 45°, but this is rarely seen, and I wonder if there's a good reason for it.
If you have a countertop in strips, the kitchen itself is rarely so exclusive that you deliver boards 45 degrees and ready. It's just about the meter!
One of my Poggenpohl kitchens I installed had an ash countertop and even there it was "Larsas'" solution.
I've never experienced a delivered countertop with 45 degrees.
It's probably also about warranty.
Is there any good way to join countertops that aren't going at an angle? We don't want to pay an extra 2500:- for a custom-ordered countertop and are thinking of joining 2 that form a long straight piece. Surely this should be much simpler?
Quite simple with the help of a router, routing jig, and a Festool Domino or a biscuit joiner. You thus route in two so-called "DogBones" to be able to join the board, biscuits, or Dominos to get an even top side.
DogBones:
What type of board do you intend to use? Laminate, wood?