Des Moines started in a backyard, with a core group of folks, playing the game with stacking rules, and having invitational BBQ tournaments for a Leinenkugel's trophy. We didn't even consider that kubb could grow outside the backyard....until we went to the US National Championship for the first time.
That's when the passion to get more people interested started for me. I felt there were really three kinds of kubb environments; people looking for events to display their skills in a competitive environment, those that relate to the game through their culture and heritage, and those simply looking to toss some lumber with the family in the backyard. And they are not mutually exclusive. A person might be looking for one, two or three of those depending on the day.
To get more people interested, and keep those interested engaged, you need to host events and environments that cater to these three categories.
NEW and RECREATIONAL:
It is a lot easier to ride on the coattails of other events to gain interest locally. We play kubb at a winery that hosts a summer concert series weekly. 100's of people see the game weekly; we encourage people just watching to jump in and play, and we hand out little cards with our website for rules, directions on how to make sets, and to our events calendar.
We have hosted learn and plays at restaurants and coffee shops that have enough green space to accommodate a pitch or two. This is no skin of their back, as they will generally get the lunch business, or some coffee sales, just from the club. Patrons then come out to see what is going on; it works out great.
Find events in the area you can reach out to that have similar ties to Scandinavian culture and/or Swedish/Norwegian groups. We have provided learn and plays to the Daughters of Norway and a group called the Valborg Vikings. Find local stores that celebrate the culture. A great example here in Des Moines is our extension of learn and plays to a winery owned by an amazing Swedish Family.
If you have a way to get into a college campus, do it. If you can get kubb to become the quintessential drinking game on frat row, you will have done your job growing the game.
This is where Des Moines can really learn from Eau Claire, WI, Chaska and Decorah Nordic Fest (I'm sure there are more). Reach out to the schools and see if you can provide learn to play events for the kids. Find ways to integrate kubb into the educations system. Get kids involved and you have a kubb player potentially for a long time.
Host a tournament, setup a rankings system locally, have leagues, find ways to get those involved to find a partner and play.
At the end of the day, you don't need to be neurotic about kubb to be successful. However, it is something that is built and takes some time investment; it is not something where kubb players will just fall in your lap. It's still a sport most people don't even know exist, so you are competing with other interests they already commit their time and money to. Don't give up, and look at a long term plan. Don't try to bite too much off if you are starting; just look to improve upon each year and scale up as interest rises.
Just my 2cents.