As gig work becomes more and more popular, employers are facing a new problem: managing a mixed workforce. In an April survey of 600 HR decision makers conducted by Field Nation and Workplace Trends, 93 percent said they have a blended workforce in which freelance workers and full-time employees team up and complete projects together.

But the reviews were mixed -- 38 percent said freelancers had great teamwork skills, while 32 percent said teamwork was a major skill they lacked.

When employees work from different locations at different times, collaboration can be a challenge, but it is possible. It’s up to managers to improve teamwork and help gig workers and full-timers work together. Here’s how:

1. Set working hours.

The ways freelancers and full-time employees work are at odds. While most employees work set hours from one location, gig workers can work any time, any place. They may work odd hours, their schedule might change from day to day, or they might not be tied down by hours at all -- they’re only required to turn in their work on time.

But if freelancers are working together with full-time employees, hours are more important. After all, HR professionals in the Field Nation and Workplace Trends survey said their top concern with managing freelancers was their availability. When working on a team, both freelancers and employees need to know when everyone will be available to collaborate, when everyone can be reached for questions, and when to expect completed assignments.

Although freelancers value flexible work, set ground rules to make a blended workforce work. Set a schedule for gig workers and keep everyone updated on their working hours. Make sure there are at least a few hours of overlap when freelancers and employees are working at the same time to make collaboration possible.

Related: W-2 or 1099? Why It Pays to Classify Your Employees Correctly.

2. Facilitate better communication.

Communication is a huge factor in the success of any team, but it’s especially important in a blended workforce where team members may never actually work face-to-face. However, HR professionals surveyed by Field Nation and Workplace Trends listed written communication skills as the top weakness among freelance workers.

Freelancers aren’t the only ones who lack communication skills -- improvement is needed on both ends. Among virtual employees surveyed by Interact in October 2014, 69 percent said the kind of communication that could keep them engaged in their work is lacking. What’s more, 55 percent said their boss communicated almost exclusively by email.

But email can’t keep up with a blended workforce. In fact, 23 percent of workers in the U.S., U.K., and Germany surveyed by Unify this year said communication tools take too long.

Face-to-face communication is still the best way for teams to collaborate, but it isn’t always possible in a blended workforce. Employees need tools that allow them to collaborate and communicate in real-time to avoid the back and forth of email.

One such example is Nuclino, which allows team members to collaborate and share information in real-time. It eliminates the need for slow messages and commenting in documents, making teamwork more efficient. And effective collaboration is essential to keep employees happy and projects moving.

Related: 5 Reasons You Should Join the Sharing Economy Revolution

3. Establish clear responsibilities.

In the office, employees can hash out who is doing it what, and can always check in with one another. But a blended team doesn’t have that luxury. And when tasks are unclear, it can cause major delays and major stress.

In a survey of 1,400 office workers published by Wrike in October 2015, respondents rated a lack of clear responsibilities among the top workplace stressors. In addition, 49 percent of employees said that waiting for other people’s actions was their most common productivity roadblock.

If responsibilities are unclear, employees could end up waiting on a task from a freelancer -- while the freelancer doesn’t know they’re supposed to handle it. By the time they get on the same page, a day has passed.

At the start of projects, clearly define who will be doing what so no one is left waiting around for no reason. Get the whole team together in a conference call to set expectations, go over deadlines, and outline how the project will progress from start to finish.

Related: How to Foster Company Culture with Remote Employees

4. Define standards.

Full-time employees understand the company mission and brand standards, and they’re deeply familiar with the working process. But freelancers don’t undergo the same onboarding and training process. They work with different employers and have developed their own way of doing things.

But when they collaborate with full-time employees, their working styles may clash, and freelancers may not be familiar with terms used internally, which can be confusing. That means employees may be left to update their work so it meets brand standards.

Although freelancers are experts, they’re not experts on the brand, the Field Nation and Workplace Trends survey suggests. Managing a consistent brand experience was among the top concerns of working with freelancers.

Before freelancers start working on the same team with full-time employees, give them a crash course on brand standards, guidelines, and internal lingo. That way, everyone is on the same page and speaking the same language when collaborating on projects.