Obviously, there's a lot of methods depending on what starting materials you have in hand. One would be to couple an amidoxime with a carboxylic acid with 2 eq. T3P and 2 eq. tea in dioxane. Start it at room temperature and warm to 80°C to perform the condensation. Add water to cristalize the product out. Whatever method you envision, try to use solvents that mixes with water so you can easily crash you your product. saves lots of time when scaling-up.

Comprehensive Heterocyclic Chemistry III

Chap.5.04

A.R. Katritzky et al

2008 Elsevier

Chap 5.04.9 by K.H. Hemming

Ring Syntheses of Fully Conjugated 1,2,4-oxadiazoles