I have advised a number of Clarity members on this question exactly. LinkedIn can be a great place to find your technical cofounder. I would look for someone who has been at their current company longer than 18 months and has relevant experience or interest in the problem you're looking to solve. Reaching-out "cold" can work, if you keep your message short and relevant.

Here's what a technical cofounder will need to see in order to feel comfortable joining you:
1) That you can fund and/or have raised sufficient money to cover the expenses up to and past launching the first version of your product.
2) That - in their assessment - you have what it takes to raise multiple rounds of funding (if the business is reliant on VC) or that you have what it takes to successfully bootstrap the business.
3) That you are realistic or at least credible in your assessment of the opportunity and have done sufficient customer development to ensure there is a viable market for your product or service.
4) That you and the technical cofounder have sufficient personal chemistry so as to want to and be able to survive an incredibly stressful and emotionally intensive journey together.

Happy to talk you through any of this in detail in a call and go into the specifics related to your location, background, and type of product or service you're looking to recruit a cofounder to.