Kyrgyzstan, since 1992
The crossed lines on the flag are a tündük, which is the top part of a Kyrgyz yurt. I’m not 100% positive but I believe that makes this the world’s first and only yurt-based flag.
As far as post-Soviet flag design goes this is one of the better examples. Apparently the flag was originally supposed to be blue and white, but it was thrown out because in some parts of southern Kyrgyzstan blue is the colour of mourning, and southern MPs wanted to lodge a protest against the all-northern composition of the flag design group. In the end the old Communist red and yellow won out. Would have looked better the other way but still an excellent symbol.
Apparently there was another proposal for a flag that had “blue, white, orange and green” with the tunduk in the top right corner. How exactly that would have worked I don’t know
(designers: Edil Aidarbekov, Bekbosun Zhaichybekov, Sabyr Iptarov, Zhusup Matayev, Mamatbek Sydykov)