Planting trees on a slope

Hi everyone. I am brand new here and in desperate need of advise! My backyard in on quite a slope and I am wondering about the best method for planting flowering trees. Swales seem like a good idea, but this is a yard and all those waves.... I could fill it in with rock maybe to keep the surface even... Or should I set each tree into the ground at the lower-edge level and kind of sink it into a hole to catch runoff rainwater. As you can see I am quite clueless!

It depends on how steep the slope is. but almost all traditional agriculture terraced the slope.
I know that this is a lot of work but you will limitthe fertilizer soil and water runoff and it is easier to harvest the fruit.
They did this in Asia in South America and traditional wineyards were terraced too.

How big/old are the trees? If they're young whips, just plant them in the ground using good standard tree planting techniques - root flare even with the ground level, roots spreading radially away from the trunk, things like that. Once the tree has established (give it a year) you can stake it to straighten it out or let nature do it's thing and over time the tree will follow its natural tendency to grow up.

If it's bigger, you can excavate the planting hole, making a level area for the tree buy using some of the uphill soil to build up the downhill side of planting area. Try for a planting area 2-3 times the size of the root ball of the tree. Don't mound the soil in a full circle around the planting area like you might on a level site, only mound the soil (2"-3") on the downhill side of the planting area - a mound on the uphill side of the pit diverts runoff away from the root zone, instead of capturing it like we want to.