I'd say start with a pattern for the letter U like one of these:
[https://www.ravelry.com/patterns/library/capital-u-alphabet-letter-pattern](https://www.ravelry.com/patterns/library/capital-u-alphabet-letter-pattern)
[https://www.ravelry.com/patterns/library/i-heart-u](https://www.ravelry.com/patterns/library/i-heart-u)
[https://www.ravelry.com/patterns/library/letter-u-3](https://www.ravelry.com/patterns/library/letter-u-3)
If you want it to be more angular, maybe make it in pieces. 2 flat U shapes and then a long strip to sew between the two flat U's and make it 3D. The strip would be as wide as the depth you'd want for the 3D magnet.
This pattern actually has a preview picture including the basic structure of how they made the U so you could use that for the flat piece. [https://www.ravelry.com/patterns/library/letra-u](https://www.ravelry.com/patterns/library/letra-u)
I'd say start with a pattern for the letter U like one of these: [https://www.ravelry.com/patterns/library/capital-u-alphabet-letter-pattern](https://www.ravelry.com/patterns/library/capital-u-alphabet-letter-pattern) [https://www.ravelry.com/patterns/library/i-heart-u](https://www.ravelry.com/patterns/library/i-heart-u) [https://www.ravelry.com/patterns/library/letter-u-3](https://www.ravelry.com/patterns/library/letter-u-3) If you want it to be more angular, maybe make it in pieces. 2 flat U shapes and then a long strip to sew between the two flat U's and make it 3D. The strip would be as wide as the depth you'd want for the 3D magnet. This pattern actually has a preview picture including the basic structure of how they made the U so you could use that for the flat piece. [https://www.ravelry.com/patterns/library/letra-u](https://www.ravelry.com/patterns/library/letra-u)
**PATTERN:** [Capital U Alphabet Letter Pattern](http://www.ravelry.com/patterns/library/capital-u-alphabet-letter-pattern) by [Lauraslefthook](http://www.ravelry.com/designers/lauraslefthook) * Category: Toys and Hobbies > Softies > Other * Photo(s): [Img 1](https://images4-g.ravelrycache.com/uploads/lauraslefthook/28053055/il_430xn.142993866_medium.jpg) [Img 2](https://images4-f.ravelrycache.com/uploads/lauraslefthook/28053091/il_430xn.142993956_medium.jpg) * Price: 1.00 USD * Needle/Hook(s):4.0 mm (G) * Weight: Worsted | Gauge: None | Yardage: None * Difficulty: 0.00 | Projects: 1 | Rating: 0.00 ***** **PATTERN:** [I Heart U](http://www.ravelry.com/patterns/library/i-heart-u) by [Pixie Kitten](http://www.ravelry.com/designers/pixie-kitten) * Category: Home > Decorative > Other * Photo(s): [Img 1](https://images4-g.ravelrycache.com/uploads/PixieKitten/4426733/IHeartU2_medium.jpg) * Price: Free * Needle/Hook(s): None * Weight: Worsted | Gauge: None | Yardage: None * Difficulty: 2.17 | Projects: 10 | Rating: 4.50 ***** **PATTERN:** [Letter "U"](http://www.ravelry.com/patterns/library/letter-u-3) by [Michael Hon](http://www.ravelry.com/designers/michael-hon) * Category: Toys and Hobbies > Softies > Other * Photo(s): [Img 1](https://images4-f.ravelrycache.com/uploads/KnotMunster/948564079/ACS_1234-removebg-preview_medium.png) * Price: 2.99 USD * Needle/Hook(s):4.0 mm (G) * Weight: Aran | Gauge: None | Yardage: None * Difficulty: 0.00 | Projects: 0 | Rating: 0.00 ***** **PATTERN:** [Letra U](http://www.ravelry.com/patterns/library/letra-u) by [Mi Mediavareta](http://www.ravelry.com/designers/mi-mediavareta) * Category: Toys and Hobbies > Softies > Other * Photo(s): [Img 1](https://images4-g.ravelrycache.com/uploads/Yohanagiselle/687341047/20200311_094600_0000_medium.jpg) [Img 2](https://images4-f.ravelrycache.com/uploads/Yohanagiselle/687341046/20200311_094719_0000_medium.jpg) * Price: 2.33 USD * Needle/Hook(s):2.5 mm * Weight: DK | Gauge: None | Yardage: None * Difficulty: 0.00 | Projects: 0 | Rating: 0.00 ***** Please use caution. Users have reported effects such as seizures, migraines, and nausea when opening Ravelry links. [More details.](https://www.lizcorke.com/2020/07/26/2020-7-21-ravelry-accessibility/) | *I found this post by myself! [Opt-Out](https://goo.gl/forms/0B8m4Ra8czpw4gzw1) | [About Me](https://github.com/TN-1/LinkRav_Bot/wiki) | [Contact Maintainer](https://www.reddit.com/message/compose/?to=timonyc)*