There are a few major issues with your design that we could fix to make it work.

• your feet connect to the frame at a right angle. You’re concentrating all the forces on a single layer line that would easily fail. Spread the forces by adding a fillet between the feet and the frame
• your vertical and free standing parts are waaaaay too thin. From empirical observation, I’d say anything free standing under 5mm thickness is guaranteed to fail. You could easily add bulk by using a triangular or U-shaped cross section. Not only the part will be much more solid, but also more stable while printing.
• As others have said, if you absolutely want to keep it thin, print the frame separately from the feet flat on the back so the forces are perpendicular to the layers. A V-shaped groove will print without supports. 45degs will be fine, depending on your printer you might event get away with shallower angles.
• if you want to keep it as a single part, you might consider printing it at 45 degrees from vertical. Layers would have much more surface area compared to the current flimsy ones, and you might even not need as much bulk as vertical printing. Most usual forces would be spread at 45 degrees too, which, while not ideal, would be much more solid than parallel from them.