We dont know the exact rules for the game(s) played on the board commonly called the Royal game of UR. Some ideas for rules can be found here. There is a tablet describing a variation but I'm having a hard time reading it.
I suspect there are many different games to be played on this board but the variety of popular rules seem to be (what I would call) children's versions. I failed to find anyone describe interesting rules for the many interesting squares on the board. I therefore think a grown-ups version is called for.
I suggest the following rules for it
The game is played with 3 or 4 two sided dices and each player gets 7 pieces.
The pieces enter the board on the far left and may start on any of the 3 sqares there.
After throwing the dices a single piece is moved by that amount of squares.
The pieces maybe be moved in all directions.
You may have only 1 piece on a field.
Moving a piece to a field occupied by the opponent removes opponents piece from the board (hereon revered to as" taken") Taken pieces have to start from the beginning.
To win the game one has to move all 7 pieces from the left to the right of the board. Pieces have to exactly move off the board. (e.g. if you are on the edge you have to throw an 1 to finish)
The starting bet is zero.
If you land a piece on a rosetta (the flower thingy) you get an extra turn after this one. Pieces on rosettas can not be taken.
The fields with 4 eyes on them are neutral, if your piece is taken here it is just taken and has no further implications.
If your piece is taken from a field with dots on it you have to add that amount of money to the ante. The center left is 12, the ones with 5 dots are 5.
If your piece is taken from a field with a jagged line around the dots you have to pay the opponent that amount directly.
This payment may be made in money OR one can move pieces that made it past the finish line back to the start. Each piece counts as 5 coins.
If for example 4 out of your 7 pieces made it cross the finish line one can avoid paying 20 Euro by putting them back at the start. As this 20 Euro could be more than the ante losing the game to avoid having to pay it could be worth it. Also, having 4 more pieces at the start makes it much more likely for things to be taken there. Controlling the rosetta and eye squares creates opportunities to force the opponent into unattractive trades.
I think with these rules the game becomes very challenging. Not knowing how much money you are going to lose seriously adds to the rage factor. Your opponent could be emptying his pockets into the ante while you've contributed nothing to it or even took some direct payments.